Exposure apparatus, optical projection apparatus and a method for adjusting the optical projection apparatus

ABSTRACT

An exposure apparatus having a plurality of projection optical systems where each of the projection optical systems projects a predetermined pattern onto a substrate and forms an exposure field on the substrate. The exposure apparatus also includes a substrate stage which holds the substrate and which moves in at least a scanning direction extending in a straight line. The plurality of exposure fields are arranged along a direction crossing the scanning direction, and the projection optical systems and the substrate relatively move during a pattern projecting operation along the scanning direction.

This is a Continuation of application Ser. No. 09/722,516 filed Nov. 28,2000, now U.S. Pat. No. 6,556,278 which in turn is a Division ofapplication Ser. No. 09/173,530 filed Oct. 15, 1998 (now U.S. Pat. No.6,351,305 B1), which is a Continuation of application Ser. No.08/991,923 filed Dec. 16, 1997 (abandoned), which is a Continuation ofapplication Ser. No. 08/453,538 filed May 30, 1995 (now U.S. Pat. No.5,729,331), which is a Continuation-in-Part of application Ser. No.08/391,944 filed Feb. 21, 1995 (now abandoned), which is a Continuationof application Ser. No. 08/259,771 filed Jun. 14, 1994 (now abandoned).The entire disclosure of the prior application(s) is hereby incorporatedby reference herein in its entirety.

RELATED APPLICATIONS

This is a Continuation-In-Part application of application Ser. No.08/259,771 filed on Jun. 14, 1994, now pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exposure apparatus, and moreparticularly to a scanning projection exposure apparatus which performsexposure while moving a first object and a second object.

2. Related Background Art

Liquid crystal display panels are frequently used these days as adisplay device for word processors, personal computers, televisions,etc. A liquid crystal display panel is fabricated by patterning oftransparent thin-film electrodes in a desired shape on a glass substrateby the photolithography technique. As an apparatus for the lithography amirror projection type aligner is used for exposure-printing an originalpattern formed on a mask onto a photoresist layer on a glass substratethrough a projection optical system.

FIG. 1 and FIG. 2 are drawings to show the structure of a conventionalmirror projection type aligner. FIG. 1 is a perspective view to show theoverall structure of the aligner and FIG. 2 is a lens cross-sectionalview to show the structure of a projection optical system in thealigner.

In FIG. 1, an illumination optical system not shown illuminates a mask71 c in an arcuate illumination field 72 a. An optical path of lightfrom the illumination field 72 a is deflected 90° by a first reflectingsurface 73 a of a trapezoid mirror 73, as shown in FIG. 2, and the thusdeflected light advances via a concave mirror 74 and a convex mirror 75and then is reflected again by the concave mirror 74. The optical pathof the light reflected by the concave mirror 74 is deflected 90° by asecond reflecting surface 73 b of the trapezoid mirror. Then an image ofthe mask 71 c or an image 72 b of the illumination field 72 a is formedon a plate 76.

The aligner as shown performs the so-called scanning exposure whilemoving the plate 76 and the mask 71 c in the X direction in thedrawings, whereby a circuit pattern on the mask 71 c is transferred ontoa selected region on the plate 76.

There is a recent demand to increase the size of liquid crystal displaypanels with such a demand to increase the size, the above-describedaligner is also desired to enlarge the exposure area.

In order to meet the demand to enlarge the exposure area, theconventional exposure apparatus as described above employed a method ofexposure with exposure area as divided into pieces. Specifically, asshown in FIG. 1, an exposure area on the plate 76 is divided into fourregions of 76 a to 76 d, and with scanning exposure of mask 71 a andregion 76 a a circuit pattern of mask 71 a is transferred onto theregion 76 a. In the next place, the mask 71 a is exchanged for anothermask 71 b and the plate 76 is moved stepwise in the XY plane in FIG. 1before a region 76 b comes to coincide with the exposure area of theprojection optical system. With scanning exposure of mask 71 b andregion 76 b, a circuit pattern of mask 71 b is then transferred onto theregion 76 b. After that, the same step is repeated for masks 71 c and 71d and regions 76 c and 76 d, whereby circuit patterns of masks 71 c and71 d are transferred onto corresponding regions 76 c and 76 d.

In such exposure with divided exposure area, the multiple scanningexposure steps must be taken for a single exposure area, which decreasesthe throughput (an exposed substrate amount per unit time). Further, incase of the partition exposure, there are seams or stitches between twoadjacent exposure regions and, therefore, the stitching accuracy must beenhanced. Because of this requirement, the method had such disadvantagesthat the magnification error of projection optical system must bedecreased as close to 0 as possible, that the alignment accuracy must begreatly improved, and that the production cost of the apparatus isincreased.

On the other hand, it can be conceivable that the scale of projectionoptical system is increased for full scanning exposure of a single largeexposure area instead of the partition exposure. In order to increasethe scale of projection optical system, however, large-scale opticalelements must be produced with very high accuracy, which results inincreasing the production cost and the size of apparatus. Also, therewas a disadvantage that the size increase of projection optical systemcaused an increase in aberrations or a decrease in imaging performance.

SUMMARY OF THE INVENTION

The present invention has been accomplished taking the above problemsinto consideration and an object of the present invention is to providean exposure apparatus which can realize full scanning exposure of alarge exposure area with excellent imaging performance and withoutlowering the throughput.

The above object and other objects will be further apparent form thefollowing description.

Provided according to the present invention is an exposure apparatusfor, while moving a first object and a second object in a certain movingdirection, effecting projection exposure of an image of said firstobject onto said second object, comprising a first projection opticalsystem for forming a real-size erect image of said first object on saidsecond object, which is telecentric at least on an image side, a secondprojection optical system for forming a real-size erect image of saidfirst object on said second object, which is telecentric at least on theimage side and which is disposed next to said first projection opticalsystem, a first field stop for limiting an exposure region to be formedon said second object by said first projection optical system, within acertain shape, and a second field stop for limiting an exposure regionto be formed on said second object by said second projection opticalsystem, within a certain shape, wherein a sum of a length along saidmoving direction, of the first exposure region limited by said firstfield stop and a length along said moving direction, of the secondexposure region limited by said second field stop is constant over adirection perpendicular to said moving direction.

In the present invention, a scanning exposure apparatus performs suchprojection exposure that a real-size erect image (which is an image withpositive horizontal and vertical lateral magnifications) of a circuitpattern formed on a mask as a first object is transferred through aplurality of projection optical systems onto a plate as a second object.A plurality of exposure regions formed on the plate through therespective projection optical systems are so arranged that a sum oflengths along the scanning direction is constant over the directionperpendicular to the scanning direction, that is, that an amount ofexposure light becomes constant over the entire surface of plate.

Since the plurality of projection optical systems are so arranged thatthe sum of widths of exposure regions along the scanning direction isconstant over the direction perpendicular to the scanning direction,single scan exposure can achieve a large exposure area on the whole evenwith compact projection optical systems and small exposure regionsformed thereby.

Also, since each projection optical system is compact, scanning exposurecan be made while minimizing occurrence of aberrations and keepingexcellent imaging performance.

In case that each projection optical system is composed of two partialoptical systems and that each exposure region formed on the plate isdefined by the shape of an aperture in a field stop located at aposition where an intermediate image of mask pattern is formed through afirst partial optical system, a preferable arrangement is such thatedges of the aperture are triangular and overlap with triangular edgesof adjacent apertures in the scanning direction.

In case that the partial optical systems are Dyson optical systems, thecenter portion of each aperture excluding the both edges thereof ispreferably defined by two straight lines. In case that the partialoptical systems are Offner optical systems, the center portion ispreferably defined by two arcs or by two polygonal lines.

It is further object of the present invention to provide an exposureapparatus for, while moving a first object and a second object in acertain moving direction, effecting projection exposure of an image ofthe first object onto the second object, comprising:

a first projection optical system for forming a real-size erect image ofthe first object on the second object, which is both-side telecentric;and

a second projection optical system for forming a real-size erect imageof the first object on the second object, which is both-side telecentricand which is disposed next to the first projection optical system;

wherein each of the first and second projection optical systems has arefractive optical system of a positive refractive power and a planereflective surface for reflecting light from the refractive opticalsystem back to the refractive optical system.

It is further object of the present invention to provide an exposureapparatus for, while moving a first object and a second object in acertain moving direction, effecting projection exposure of an image ofthe first object onto the second object, comprising:

a first projection optical system for forming an erect image of thefirst object on the second object; and

a second projection optical system for forming an erect image of thefirst object on the second object, which is disposed next to the firstprojection optical system;

wherein each of the first and second projection optical systems has:

a first image-forming optical system arranged so that one of twoconjugate points is located on the first object; and

a second image-forming optical system arranged so that one of twoconjugate points is coincident with the other conjugate point of thefirst image-forming optical system and so that the other of the twoconjugate points is located on the second object;

wherein either one of the first image-forming optical system and secondimage-forming optical system is an Offner optical system having aconcave reflective mirror and a convex reflective mirror and arranged toguide light from one conjugate point to the other conjugate point whilereflecting the light by the concave reflective mirror, the convexreflective mirror, and the concave reflective mirror in the named order;and

wherein the other of the first and second image-forming optical systemsis a Dyson optical system having first and second reflective prisms, alens group of a positive refractive power, and a concave reflectivemirror with a concave surface to the lens group and arranged to guidelight from one conjugate point to the other conjugate point via thefirst reflective prism, the lens group, the concave reflective mirror,the lens group, and the second reflective prism in the named order.

It is further object of the present invention to provide a projectionoptical system for forming an image of a first object on a secondobject, a projection optical apparatus comprising:

an optical system having an optical axis and at least one reflectivesurface coaxial with the optical axis;

first light splitting means disposed in an optical path between theoptical system and the first object; and

second light splitting means disposed in an optical path between theoptical system and the second object;

wherein a light beam passing the second light splitting means istransferred along a direction traversing the optical axis to be guidedto the first light splitting means.

It is further object of the present invention to provide an exposureapparatus for, while moving a first object and a second object in acertain moving direction, effecting projection exposure of an image ofthe first object onto the second object, comprising:

a first reflective surface for deflecting light coming from the firstobject;

an image-forming optical system for forming an intermediate image of thefirst object, based on light coming from the first reflective surface;

a beam transferring member for transferring the light of from the firstreflective surface and then through the image-forming optical system,along a direction traversing an optical axis of the image-formingoptical system to guide the thus transferred light again to theimage-forming optical system; and

a second reflective surface for deflecting the light of from the beamtransferring member and then through the image-forming optical system,to the second object.

It is further object of the present invention to provide an exposureapparatus for, while moving a first object and a second object in acertain moving direction, effecting projection exposure of an image ofthe first object onto the second object, comprising:

a first projection optical system for forming an erect image of thefirst object on the second object; and

a second projection optical system for forming an erect image of thefirst object on the second object, which is disposed next to the firstprojection optical system;

wherein each of the first and second projection optical systemscomprises:

a first reflective surface for deflecting light from the first object;

an image-forming optical system having an optical axis and two conjugatepoints, the image-forming optical system being disposed so that thefirst reflective surface is positioned on a side of one conjugate pointout of the two conjugate points, and the image-forming optical systembeing for forming an intermediate image of the first object, based onlight coming from the first reflective surface;

a beam transferring member for transferring the light of from the firstreflective surface and then through the image-forming optical system,along a direction traversing the optical axis of the image-formingoptical system to guide the thus transferred light again to theimage-forming optical system; and

a second reflective surface for deflecting the light of from the beamtransferring member and then through the image-forming optical system,to the second object.

It is further object of the present invention to provide a projectionoptical apparatus comprising:

an image-forming optical system having an optical axis and two conjugatepoints;

a field splitting member disposed on a side of one conjugate point ofthe projection optical system, for splitting a field of the projectionoptical system; and

a beam transferring member disposed on a side of the other conjugatepoint of the projection optical system, for transferring light passingvia the field splitting member and the projection optical system in thenamed order, along a direction traversing the optical axis of theprojection optical system.

It is further object of the present invention to provide an exposureapparatus for, while moving a first object and a second object in acertain moving direction, illuminating the first object by anillumination optical system and effecting projection exposure of animage of the first object onto the second object by a projection opticalsystem a position of which is fixed relative to the illumination opticalsystem:

wherein the illumination optical system comprises:

a first illumination optical system for forming a first illuminationregion on the first object; and

a second illumination optical system for forming a second illuminationregion different from the first illumination region on the first object;

wherein the projection optical system comprises:

a first projection optical system for forming an erect image of thefirst object illuminated by the first illumination optical system on thesecond object; and

a second projection optical system for forming an erect image of thefirst object illuminated by the second illumination optical system onthe second object;

wherein the first illumination optical system comprises firstillumination region moving means for moving the first illuminationregion on the first object relative to the first projection opticalsystem; and

wherein the second illumination optical system comprises secondillumination region moving means for moving the second illuminationregion on the first object relative to the second projection opticalsystem.

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not to beconsidered as limiting the present invention.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view to show the overall structure of aconventional mirror projection type aligner;

FIG. 2 is a side view to show the structure of a projection opticalsystem in the conventional mirror projection type aligner;

FIG. 3 is a perspective view to show the overall structure of anexposure apparatus in an embodiment of the present invention;

FIG. 4 is a perspective view to show an example of an illuminationoptical system applied to the exposure apparatus of the presentinvention;

FIG. 5 is a perspective view to schematically show another example ofillumination optical system;

FIG. 6 is a side cross section of a projection optical system applied tothe exposure apparatus in the embodiment of the present invention;

FIG. 7 is a side cross-sectional view to show another example ofprojection optical system;

FIG. 8 is a plan view to show a field stop having a trapezoid aperture;

FIG. 9 is a drawing to show a planar positional relation between thetrapezoid aperture and a maximum field region by a Dyson optical system;

FIG. 10 is a plan view to show a field stop having a hexagonal aperture;

FIG. 11 is a drawing to show a planar positional relation between thehexagonal aperture and a maximum field region by a Dyson optical system;

FIG. 12 is a drawing to show a planar positional relation between fieldregions by projection optical systems and a mask;

FIG. 13 is a drawing to show distributions of exposure for the Ydirection on a plate;

FIG. 14 is a plan view to illustrate a layout of a plurality of Dysonprojection optical systems;

FIG. 15, FIG. 16 and FIG. 17 are lens constitutional drawings to showanother example of Dyson projection optical system;

FIG. 18 is a perspective view to show the overall structure of anexposure apparatus in the second embodiment of the present invention;

FIG. 19 is a side partial cross-sectional view of a projection opticalsystem applied to the exposure apparatus in the second embodiment ofFIG. 18;

FIG. 20 is a plan view to show a field stop having an aperture witharcuate borders;

FIG. 21 is a drawing to show a planar positional relation between theaperture with arcuate borders and a maximum field region by an Offneroptical system;

FIG. 22 is a plan view to show a field stop having an aperture withpolygonal borders;

FIG. 23 is a drawing to show a planar positional relation between theaperture with polygonal borders and a maximum field region by an Offneroptical system;

FIG. 24 is a drawing to show a planar positional relation between fieldregions by Offner projection optical systems and a mask;

FIG. 25 is a side view to show another example of Offner projectionoptical system;

FIG. 26 is a plan view to illustrate a layout of a plurality of Offnerprojection optical systems;

FIG. 27 is a side cross-sectional view to show a third embodiment of aprojection optical system applied to the exposure apparatus according tothe present invention;

FIGS. 28A to 28C are drawings to show a planar positional relationbetween an exposure region and a field stop of the third embodiment;

FIG. 29 is a perspective view to show the overall structure of theexposure apparatus in which the projection optical system of the fourthembodiment is applied;

FIG. 30 is a side cross-sectional view to show the fifth embodiment of aprojection optical system applied to the exposure apparatus;

FIG. 31 is a perspective view of a reflective member 513 used in thefifth embodiment of the projection optical system;

FIGS. 32A to 32C are planar views to show some modification of a fieldstop used in the third, fourth and fifth embodiment of the projectionoptical system;

FIG. 33 is a side cross-sectional view to show a sixth embodiment of aprojection optical system applied to the exposure apparatus according tothe present invention;

FIG. 34 is a planar view to show arrangement of exposure regions on aplate in the exposure apparatus in which the projection optical systemof the sixth embodiment is applied;

FIGS. 35A to 35E are drawings for explanation of a field of the sixthembodiment of the projection optical system;

FIG. 36 is a a drawing to show the planar positional relationshipbetween the exposure regions and fields in the sixth embodiment of theprojection optical system;

FIG. 37 is a perspective view to schematically show the modification ofthe sixth embodiment of the projection optical system;

FIGS. 38A to 38E are drawings for explanation of the field in the sixthembodiment and the modification thereof the projection optical system;

FIG. 39 is a side cross-sectional view to show the structure of theseventh embodiment of the projection optical system;

FIG. 40 is a planer view to explain an exposure operation in the seventhembodiment;

FIG. 41 is a side cross-sectional view to show the structure of thefirst modification of seventh embodiment of the projection opticalsystem;

FIGS. 42A and 42B are side cross-sectional views to show the structureof the second modification of the seventh embodiment of the projectionoptical system and a field thereof;

FIG. 43 is a side cross-sectional view to show the structure of thethird modification of the seventh embodiment of the projection opticalsystem;

FIG. 44 is a side cross-sectional view to show the structure of thefourth modification of the seventh embodiment of the projection opticalsystem; a;

FIG. 45 is a side cross-sectional view to show the is structure of thefifth modification of the seventh embodiment of the projection opticalsystem; a;

FIG. 46 is a perspective view of the exposure apparatus to which thesixth modification of the seventh embodiment of the projection opticalsystem is applied;

FIG. 47 is a perspective view of the preferred illumination system forthe sixth modification of the seventh embodiment;

FIG. 48 is a drawing to show the preferred illumination the exposureapparatus in which the seventh modification of the sixth embodiment ofthe projection optical system is incorporated;

FIG. 49 is a side cross-sectional view to show the eighth embodiment ofthe projection optical system according to the present invention;

FIG. 50 is a perspective view to show the exposure apparatus in whichthe projection optical system of eighth embodiment is incorporated;

FIG. 51 is a perspective view to show an another exposure apparatus inwhich the projection optical system of the eighth embodiment isincorporated;

FIGS. 52A and 52B are enlarged views of the eighth embodiment of theoptical projection system;

FIGS. 53A and 53B are drawings to show a field of the eighth embodimentof the projection optical system;

FIGS. 54A, 54B, 54C and 54D are drawings to show planar positionalrelationship between the fields and the exposure regions;

FIG. 55 is a side cross-sectional view to show the modification of theeighth embodiment of the projection optical system;

FIG. 56 is a drawing to show relationship between the magnification ofthe optical system and overlapping area in the eighth embodiment;

FIG. 57 is a side cross-sectional view to show the ninth embodiment ofthe projection optical system;

FIG. 58 is a perspective view to show an another exposure according tothe present invention;

FIG. 59 is a side cross-sectional view to show a main portion of theillumination system of the another exposure apparatus shown in FIG. 59;

FIG. 60 is a planar view to show the arrangement of illumination regionson a mask in the another exposure apparatus shown in FIG. 58;

FIG. 61 is a side cross-sectional view to show the projection opticalsystem of the exposure apparatus shown in FIG. 58;

FIG. 62 is a drawing to show the arrangement of exposure regions on aplate of the exposure apparatus shown in FIG. 58;

FIGS. 63A and 63B are drawings to show the modifications ofillumination-region transfer means and exposure-region transfer meansusable in the exposure apparatus shown in FIG. 58;

FIG. 64 is a drawing to show the modification of the field stop usablein the exposure apparatus shown in FIG. 58;

FIGS. 65A and 65B are drawings to show the modification of the fieldstop usable in the exposure apparatus shown in FIG. 58; and

FIGS. 66A and 66B are drawings to show the modification of the fieldstop usable in the exposure apparatus shown in FIG. 58.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments according to the present invention will be described withreference to the drawings. FIG. 3 is a perspective view of an exposureapparatus according to the present invention. FIG. 3 employs acoordinate system in which the X axis is taken in the direction(scanning direction) of conveyance of a mask 8 which is provided with apredetermined circuit pattern and a plate 9 in which a coating of resistis given on a glass substrate, the Y axis in the direction perpendicularto the X direction in a plane of mask 8, and the Z axis in the directionnormal to the mask 8.

In FIG. 3, exposure light from an illumination optical system 10uniformly illuminates the mask 8 in the XY plane in the drawing. Asuitable illumination optical system 10 is for example one having thestructure as shown in FIG. 4. FIG. 4 is a drawing to show an example ofspecific structure of illumination optical system 10 shown in FIG. 3. InFIG. 4, there is a light source, for example a mercury lamp supplyingexposure light of the g line (435 nm) or the i line (365 nm), inside anelliptic mirror 102, and exposure light from the light source iscollected by the elliptic mirror 102 to form an image of the lightsource on an entrance end of light guide 103. The light guide 103 formssecondary light source planes with uniform optical intensitydistribution at its exit ends 103 a, 103 b. The uniform opticalintensity distribution can be obtained by constructing the light guide103 of optical fibers as bundled at random.

Beams outgoing from the light guide 103 pass through respective relaylenses 104 a, 104 b to reach fly's eye lenses 105 a, 105 b. A pluralityof secondary light sources are formed on the exit planes of fly's eyelenses 105 a, 105 b. Light from the plural secondary light sourcespasses through condenser lenses 106 a, 106 b with the front focusthereof located at the secondary-light-sources-formed position then touniformly illuminate a field stop 107 having rectangular apertures 107a, 107 b. The exposure light beams passing through the field stop 107pass through respective lenses 108 a, 108 b and then are deflected 90°in optical path thereof by mirrors 109 a, 109 b to reach lenses 110 a,110 b. Here, the lenses 108 a, 110 a and the lenses 108 b, 110 b are arelay optical system for making the field stop 107 conjugate with themask 8, so that the exposure light passing through the lenses 110 a, 110b forms illumination regions 111 a, 111 b as images of the apertures 107a, 107 b in the field stop 107.

It should be noted that the shape of the apertures 107 a, 107 b in thefield stop 107 is not limited to the rectangle. It is preferred that theshape of the illumination regions is as similar to the shape of field ofprojection optical systems as possible.

FIG. 4 shows only optical axes of illumination optical systems forforming illumination regions 111 c-111 g for brevity of illustration.Although not shown in FIG. 4, exit ends of light guide 103 are setcorresponding to the number of illumination regions and exposure lightfrom the exit ends of unrepresented light guides 103 is supplied tothese illumination regions 111 c-111 g.

If a light source is insufficient in respect of a light quantity in thecase as shown in FIG. 4, the arrangement as shown in FIG. 5 may beapplied. FIG. 5 is a drawing to diagrammatically show the main part of amodification of illumination optical system, in which exposure lightfrom light sources 201 a-201 c such as mercury lamps is collected byelliptic mirrors 202 a-202 c to form light source images. A light guide203 is located with its entrance ends at the light-sources-image-formedpositions, and exposure light passing through the light guide 203 formssecondary light source surfaces with a uniform optical intensitydistribution at a plurality of exit ends 203 a-203 e. This light guide203 is also constructed of optical fibers as bundled at random,similarly as the light guide 103 in FIG. 4. The optical paths rangingfrom the exit ends 203 a-203 e to the mask 8 are the same as those inthe illumination optical system shown in FIG. 4, and therefore areomitted to explain herein. The above arrangement obtains a necessarylight quantity by adding light from low-power light sources 201 a-201 c,necessitating no use of high-power light sources complex in control andallowing the illumination system to be simply assembled.

Instead of the plurality of illumination optical systems forming theplurality of illumination regions 111 a-111 g as described above,another illumination optical system may employ such an arrangement thatthe mask 8 is illuminated in a rectangular region extending in thescanning direction (the X direction) and the direction perpendicularthereto (the Y direction). An example of such optical system is a rodlight source extending in the Y direction.

Now, there are a plurality of projection optical systems 2 a-2 g belowthe mask 8. The projection optical systems 2 a-2 g are described belowreferring to FIG. 6. Since the projection optical systems 2 a-2 g havethe same structure, only a projection optical system 2 a is describedfor brevity of description.

FIG. 6 is a lens structural drawing of the projection optical system 2a, where the projection optical system 2 a has the structure of acombination of two Dyson optical systems. In FIG. 6, the projectionoptical system 2 a is composed of a first partial optical system 21-24,a field stop 25 and a second partial optical system 26-29, and thesefirst and second partial optical systems are modified Dyson opticalsystems.

The first partial optical system has a right-angle prism 21 having areflective surface inclined at 45° relative to the surface of mask 8, aplano-convex lens component 22 with the optical axis along an in-planedirection of mask 8 and the convex surface directed toward the oppositeside of the right-angle prism 21, a lens component 23 having a meniscusshape on the whole with a reflective surface of the concave surfacedirected toward the plano-convex lens component 22, and a right-angleprism 24 having a reflective surface perpendicular to the reflectivesurface of the right-angle prism 21 and inclined at 45° relative to thesurface of mask 8.

The light from the illumination optical system through the mask 8 isdeflected 90° in optical path by the right-angle prism 21 to enter theplano-convex lens component 22 bonded to the right-angle prism 21.Bonded to this lens component 22 is the lens component 23 made of aglass material different from that of the plano-convex lens component22, so that the light from the right-angle prism 21 is refracted by ajoint surface 22 a between the lens components 22, 23 to reach thereflective surface 23 a with a vapor-deposited reflecting film. Thelight reflected by the reflective surface 23 a is refracted by the jointsurface 22 a then to reach the right-angle prism 24 bonded to the lenscomponent 22. The light from the lens component 22 is deflected 90° inoptical path by the right-angle prism 24 to form a primary image of mask8 on the exit plane side of the right-angle prism 24. Here, the primaryimage of mask 8 formed by the first partial optical system 21-24 is areal-size image for which the lateral magnification is positive in the Xdirection and negative in the Y direction in FIG. 6.

The light from the primary image passes through the second partialoptical system 26-29 to form a secondary image of mask 8 on the plate 9.The structure of the second partial optical system is the same as thatof the first partial optical system and therefore is omitted to explain.The second partial optical system 26-29 forms a real-size image forwhich the lateral magnification is positive in the X direction andnegative in the Y direction, as the first partial optical system does.Therefore, the secondary image formed on the plate 9 is a real-sizeerect image of mask 8 (an image positive in vertical and horizontallateral magnifications).

Preferably, the exposure apparatus is an optical system telecentric atleast on the image side. This is because no dimension error of actuallyexposed pattern on the wafer is caused even if the wafer for an image tobe formed is moved vertically (or if in multiple printing the wafer isvertically shifted from the position upon first exposure) or even ifthere is a large step between circuit patterns formed on the wafer.

In steppers of full exposure type the mask position is always keptunchanged, because a mask-mounting table is fixed to the main body ofexposure apparatus. Accordingly, no dimensional error of pattern iscaused even though the exposure apparatus is not telecentric on the maskside (object side).

In case of a scanning exposure apparatus, both the mask and the waferare arranged to move upon exposure, which could cause a shift ofpositional relation in the vertical direction between the mask and thewafer. Unless the exposure apparatus is constructed as a both sidetelecentric optical system, there is the possibility of change indimensions of circuit pattern image formed on the wafer. Here, the “bothside” means image side and object side. Accordingly, a both sidetelecentric optical system is preferable for the scanning exposureapparatus in the present invention, and therefore the first and secondpartial optical systems in the projection optical system 2 a are bothside telecentric optical systems.

The above-described first and second partial optical systems are soarranged that the reflective surfaces 23 a, 28 a are directed in a samedirection. This can decrease the size of the entire projection opticalsystem.

The first and second partial optical systems in the present embodimentare constructed such that a glass material fills the optical pathbetween the plano-convex lens components 22, 27 and the reflectivesurfaces 23 a, 28 a. This is advantageous in causing no offset betweenthe plano-convex lens components 22, 27 and the reflective surfaces 23a, 28 a.

Also, the first and second partial optical systems each may beconstructed as a so-called Dyson optical system itself in which airfills a space between the plano-convex lens components 22, 27 and thereflective surfaces 23 a, 28 a, as shown in FIG. 7. Such a Dyson opticalsystem is described in detail on P713-716 in J. O. S. A. vol. 49(published 1959).

In the present embodiment the field stop 25 is located at the positionof primary image formed by the first partial optical system. The fieldstop 25 has an aperture 25A for example of trapezoid as shown in FIG. 8.The field stop 25 defines a trapezoid exposure area on the plate 9.Since in the Dyson optical system in the present embodiment across-sectional profile (in the YZ plane) of lens components 22, 23, 27,28 is circular, a possible maximum field region is semi-circular asshown in FIG. 9. In this case a preferable arrangement is that thetrapezoid field region 8 a (see FIG. 3) defined by the field stop 25 isformed with a shorter side out of a pair of parallel sides being on thearc side of the semi-circular region (the maximum field region). Thisarrangement permits the width of field region in the scanning direction(X direction) to be maximized with respect to the possible maximum fieldregion of the Dyson optical system, which can increase the scanningspeed.

Also, the field stop 25 may be arranged to have a hexagonal aperture 25b as shown in FIG. 10. In this case the dimensions of the hexagonalaperture 25B drop in the range of maximum field region as represented bythe dashed line in the drawing, as shown in FIG. 11. Here, the maximumfield region shown by the dashed line in FIG. 9 or in FIG. 11 is aregion surrounded by points where rays passing through the outermostregion pass on the mask 8 out of off-axial rays passing without eclipsethrough the first and second partial optical systems.

Returning to FIG. 3, the layout of the projection optical systems 2 a-2g is described below. In FIG. 3, the projection optical systems 2 a-2 ghave field regions 8 a-8 g defined by field stops in the projectionoptical systems. Images of these field regions 8 a-8 g are formed asreal-size erect images on the exposure regions 9 a-9 g on the plate.Only when the real-size erect images are thus obtained, the exposureregions 9 a-9 g are perfectly linked.

Here, the projection optical systems 2 a-2 g are so arranged that thefield regions 8 a-8 d are aligned in the Y direction in the drawing.Also, the projection optical systems 2 e-2 g are so arranged that thefield regions 8 e-8 g are aligned along the Y direction at positionsdifferent from those of the field regions 8 a-8 d in the X direction inthe drawing. The projection optical systems 2 e-2 g are interposedbetween the projection optical systems 2 a-2 d in the Y direction.Namely, the projection optical systems are arranged in the order of 2 a,2 e, 2 b, 2 f, 2 c, 2 g, 2 d along the Y direction. In this case, theprojection optical systems 2 a-2 d and the projection optical systems 2e-2 g are so arranged that the right-angle prisms in the projectionoptical systems are located very close to each other. The projectionoptical systems 2 a-2 g may be set such that the spacing is enlargedbetween the field regions 8 a-8 d and the field regions 8 e-8 g in the Xdirection, but such an arrangement increases a scanning amount forscanning exposure (an amount of movement of the mask 8 and the plate 9)so as to cause a decrease in throughput, which is not preferable.

On the plate 9, the projection optical systems 2 a-2 d form exposureregions 9 a-9 d aligned along the Y direction in the drawing, while theprojection optical systems 2 e-2 g form exposure regions 9 e-9 g alsoaligned along the Y direction but at positions different in the Ydirection from those of the exposure regions 9 a-9 d. These exposureregions 9 a-9 g are real-size erect images of the field regions 8 a-8 g.

In this arrangement, the mask 8 is mounted on a mask stage 80 and theplate 9 is mounted on a plate stage 60. Here, the mask stage and platestage move in synchronization in the X direction in the drawing. Bythis, an image of mask 8 illuminated by the illumination optical system10 is successively transferred onto the plate 9, effecting so-calledscanning exposure. After completion of scan of the entire surface ofmask 8 by the field regions 8 a-8 g with movement of the mask 8, theimage of mask 8 is transferred over the entire surface on the plate 9.

There are provided on the plate stage 60 a reflecting member 61 having areflective surface along the Y axis and a reflecting member 62 having areflective surface along the X axis. An interferometer is set on themain body of exposure apparatus. The interferometer includes a laserbeam source 63 for supplying a laser beam for example of He-Ne (633 nm),a beam splitter 64 for splitting the laser beam from the laser beamsource 63 into a laser beam for X-directional measurement and a laserbeam for Y-directional measurement, a prism 65 for projecting the laserbeam from the beam splitter 64 onto the reflecting member 61, and prisms66, 67 for projecting the laser beam from the beam splitter 64 onto twopoints on the reflecting member 62. This arrangement permits detectionof X-directional position, Y-directional position and rotation in the XYplane of the stage. In FIG. 3, illustration is omitted for a detectionsystem for detecting interference fringes between the laser beam and thereference laser beam reflected by the reflecting members 61, 62.

The layout of the field regions in the present embodiment is nextdescribed referring to FIG. 12. FIG. 12 is a drawing to show a planarpositional relation between the field regions 8 a-8 g by the projectionoptical systems 2 a-2 g, and the mask 8. In FIG. 12, a circuit patternPA is formed on the mask 8 and a light-shielding portion LSA is providedto surround the region of the circuit pattern PA. The illuminationoptical system shown in FIG. 4 uniformly illuminates the illuminationregions 111 a-111 g surrounded by dashed lines in the drawing. Theabove-described field regions 8 a-8 g are located in the illuminationregions 111 a-111 g. These field regions 8 a-8 g each are shapedsubstantially in a trapezoid profile by the field stops in theprojection optical systems 2 a-2 g. Here, the upper edges of fieldregions 8 a-8 d (shorter sides out of parallel side pairs) are arrangedto be opposed to the upper edges of field regions 8 e-8 g (shorter sidesout of parallel side pairs). The shape of field regions 8 a and 8 dbesides the light-shielding portion LSA is so defined that the sides onthe light-shielding portion LSA side (edges other than the parallel sidepairs) coincide with the edge of region of the circuit pattern PA. Thefield regions 8 a and 8 d may be formed in a profile overlapping withthe light-shielding portion LSA of mask 8.

Since in the present embodiment the projection optical systems 2 a-2 gare both side telecentric optical systems, areas occupied by theprojection optical systems 2 a-2 g are greater than those occupied bythe corresponding field regions 8 a-8 g on the XY plane. Accordingly,the layout of field regions 8 a-8 d must be determined with spacingsbetween the respective regions 8 a-8 d. In this case, scanning exposureonly with the field regions 8 a-8 d would result in failing toprojection-transfer the regions among the field regions 8 a-8 d on themask 8 onto the plate 9. Thus, the present embodiment is so arrangedthat in order to effect scanning exposure for the regions among thefield regions 8 a-8 d as well, the field regions 8 e-8 g are formed bythe projection optical systems 2 e-2 g.

It is preferred that a sum of widths of the field regions 8 a-8 g (orthe exposure regions 9 a-9 g) along the scanning direction (X direction)is always constant at any location in the Y direction. This is describedbelow referring to FIG. 13.

FIG. 13 includes (a) and (b) to show distributions of X-directionalexposure on the plate 9, in which the vertical axis represents exposureE and the horizontal axis the Y-directional position on the plate 9. In(a) of FIG. 13, exposure distributions 90 a-90 g corresponding to therespective trapezoid exposure regions 9 a-9 g are obtained on the plate9. Since in scanning exposure the exposure regions are determined suchthat the sum of X-directional widths of exposure regions 9 a-9 g isconstant, the exposure is always constant for the superimposed regionsamong the exposure regions 9 a-9 g. For example, as for a superimposedregion between an exposure distribution 90 a corresponding to theexposure region 9 a and an exposure distribution 90 e corresponding tothe exposure region 9 e, a sum of X-directional width of exposure region9 a and X-directional width of exposure region 9 e is constant, so thatthe sum of exposures in the superimposed region becomes equal to anexposure in a non-superimposed region. Accordingly, a uniform exposuredistribution 91 is obtained over the entire surface on the plate 9, asshown in (b) of FIG. 13. Although the above description concerned thecase of trapezoid exposure regions, the combination of exposure regionsfor obtaining a uniform exposure distribution is not limited to suchtrapezoids. For example, in case a plurality of hexagonal exposureregions are formed by the field stops 25 as shown in FIG. 10, theexposure regions are so defined that the scanning-direction width of theexposure regions becomes always constant. By this, a uniform exposuredistribution can be obtained over the entire surface on the plate 9.

The field regions and the exposure regions corresponding to therespective projection optical systems may be defined such that a uniformexposure distribution can be obtained over the entire exposed surface bythe field stops 25 in the projection optical systems. As a result, theoptical system for precisely defining the field regions may be obviatedin the illumination optical system 10. In other words, the field regions8 a-8 g on the mask 8 are defined by the apertures of field stops in theassociated projection optical systems 2 a-2 g, and therefore theillumination optical system 10 necessitates no optical system forprecisely defining the field regions 8 a-8 g.

A preferable layout of the projection optical systems in the presentembodiment is next described referring to FIG. 14. FIG. 14 is a planview to illustrate an arrangement of the projection optical systems,which shows projection optical systems D₁, D₂, D₃ as seen from the mask8 side (object side). In FIG. 14, the projection optical system D₁ iscomposed of a plano-convex lens component L₁ and a concave mirror M₁,the projection optical system D₂ is of a plano-convex lens component L₂and a concave mirror M_(z), and the projection optical system D₃ is of aplano-convex lens component L₃ and a concave mirror M₃. Here, theprojection optical systems D₁, D₂, D₃ have the same structure. Forbrevity of illustration, FIG. 14 is drawn such that the optical paths ofthe projection optical systems D₁, D₂, D₃ include only optical pathsfrom the object to the concave mirrors (reflecting mirrors) M₁, M₂, M₃but exclude right-angle prisms for deflecting the optical paths in the Zdirection.

Now, let Φ_(F1) be the Y-directional width of a possible maximum fieldregion of the projection optical system D₁, Φ_(F2) be the Y-directionalwidth of a possible maximum field region of the projection opticalsystem D₂, and Φ_(F3) be the Y-directional width of a possible maximumfield region of the projection optical system D₃. These Y-directionalwidths Φ_(F1)-Φ_(F3) of the field regions correspond to the radiallength of the maximum field region as shown by the dashed straight linein FIG. 9 or FIG. 11.

Then, letting K be a distance between optical axes of the projectionoptical systems D₁, D₃ arranged next to each other in the Y direction,it is preferable that the following relation is satisfied:

Φ_(F1)/2+Φ_(F2)+Φ_(F3)/2>K  (1)

Here, substituting Φ_(F1)=Φ_(F2)=Φ_(F3)=Φ_(F) (where Φ_(F) is theY-directional width of a possible maximum field region of the projectionoptical systems), the above formula (1) can be rewritten as follows.

2Φ_(F) >K  (2)

This means that the Y-directional width Φ_(F) of the possible maximumfield region of the projection optical systems is preferably a half ormore of the distance between the optical axes of projection opticalsystems in the Y direction. If the layout of the projection opticalsystems is out of the range of the above formula (1) or formula (2),there could occur an unpreferable case. that the field regions fail tooverlap with each other in the Y direction.

Also, let Φ_(L1)-Φ_(L3) be diameters (Y-directional lengths) of theplano-convex lens components L₁-L₃, Φ_(M1)-Φ_(M3) be diameters(Y-directional lengths) of the concave mirrors M₁-M₃, and Φ_(D1)-Φ_(D3)larger diameters among them (i.e., maximum values of outer diameters ofthe projection optical systems D₁, D₂, D₃).

Since the projection optical systems D₁, D₂, D₃ have the same structure,the following relations hold:

Φ_(L1)=Φ_(L2)=Φ_(L3);

Φ_(M1)=Φ_(M2)=Φ_(M3);

Φ_(D1)=Φ_(D2)=Φ_(D3)=Φ_(D)  (3)

Letting Φ_(F) be the Y-directional width of the possible maximum fieldregion of the projection optical systems, the following relation ispreferably to be satisfied:

Φ_(F)>Φ_(D)/2  (4)

If the projection optical systems D₁-D₃ do not satisfy the above formula(4), that is, if the Y-directional width Φ_(F) of the possible maximumfield region of the projection optical systems is not greater than ahalf of the maximum value Φ_(D) of outer diameter of the projectionoptical systems, there could occur an unpreferable case that twoprojection optical systems D₁, D₃ disposed adjacent to each other in theY direction interfere with each other. In case the maximum value ofouter diameter of projection optical systems is determined by theright-angle prisms for deflecting the optical paths by 90°, the maximumvalue Φ_(D) of outer diameter is to be determined as the Y-directionallength of right-angle prisms. The above relations of formula (1) toformula (4) are not limited to the Dyson optical system but can beapplied to an Offner optical system as described later.

The above-described embodiment employed a combination of two sets ofoptical systems as the projection optical systems, but instead thereofoptical systems as shown in FIG. 15 or FIG. 16 may be applied. FIG. 15shows an example in which an Amici prism (right-angle roof prism) 34with a dach (roof) surface is employed in place of the right-angle prismin a Dyson optical system. The Amici prism functions to bend thetraveling direction of light by 90° and to invert an image left toright. In FIG. 15, a right-angle prism 31, a plano-convex lens component32 and a lens component 33 having a reflective surface 33 a have thesame functions as the right-angle prism 21, the plano-convex lenscomponent 22 and the lens component 23 shown in FIG. 6, respectively,and are omitted to explain herein. A Dyson optical system having tworight-angle prisms forms an image for which the lateral magnification ispositive in the direction along the optical axis (the X direction) andthe lateral magnification is negative in the direction perdendicular tothe optical axis (the direction along the object plane and the imageplane, i.e., the Y direction). A Dyson optical system having an Amiciprism 34 as shown in FIG. 15 inverts an image orientation in thedirection perpendicular to the optical axis (the Y direction) in theobject plane and the image plane by its dach surface, so that it canform an erect image for which the lateral magnifications is positiveboth in the direction along the optical axis (the X direction) and inthe direction perpendicular to the optical axis (Y direction) in theobject plane and the image plane.

FIG. 16 is a lens structural drawing to show an, example of Dysonoptical system provided with reflective surfaces for bending the opticalpath. In FIG. 16, light from the mask 8 is deflected 90° in optical pathby a semi-reflecting surface 41 a inclined at 45° relative to thedirection of incidence of light (the Z direction) to enter aplano-convex lens component 42. The plano-convex lens component 42 and alens component 43 bonded to the plano-convex lens component 42 shown inFIG. 16 have the same functions as the plano-convex lens component 22and the lens component 23 in FIG. 6, respectively.

The light incident into the plano-convex lens component 42 is reflectedby a reflective surface 43 a and again passes through the plano-convexlens component 42 to form a primary image of mask 8 on the exit side ofplano-convex lens component 42. Another reflective surface 41 b is setat the position where the primary image is formed. Here, thesemi-reflective surface 41 a and the reflective surface 41 b are formedon a reflecting member 41. Then the light from the primary image on thereflective surface 41 b travels backward in the same optical path toadvance through the plano-convex lens component 42 and the lenscomponent 43 and then to pass through the semi-reflective surface 41 a.On the transmission side of the semi-reflective surface 41 a there areprovided a reflecting member 44 having a reflective surface 44 ainclined at 112.5° relative to the direction of incidence of rays (thetransmission direction) and a reflective surface 44 b inclined at 45°relative to the reflective surface 44 a. Since the reflective surfaces44 a, 44 b have a function of pentagonal prism, the light incident intothe reflecting member 44 is deflected 90° in optical path throughreflection on the reflective surfaces 44 a, 44 b.

The light reflected by the reflective surfaces 44 a, 44 b forms asecondary image of mask 8 on the exit side of reflecting member 44.Here, the secondary image is a real-size erect image. In FIG. 16, theoptical path length from the mask 8 to the reflective surface 41 b isarranged to be equal to that from the reflective surface 41 b to theplate 9.

In the projection optical system shown in FIG. 16 the shape of thereflective surface 41 b is the shape of field stop. For example, in caseof a trapezoid reflecting surface. 41 b with the shorter edge in the YZplane located up on the drawing plane, the field region and exposureregion will be trapezoid with the shorter edge located right on theplane of drawing and on the XY plane in the projection optical system ofFIG. 16, rays passing near the optical axis of the plano-convex lenscomponent 42 and the lens component 43 do not reach the reflectivesurface 41 b and therefore do not contribute to image formation.However, in order to avoid mixture of the optical path from thesemi-reflective surface 41 a to the reflective surface 43 a with theoptical path from the reflective surface 41 b to the reflective surface43 a, it is rare to use rays passing on and near the optical axis of theplano-convex lens component 42 and the lens component 43. Accordingly,even if the rays passing near the optical path of the plano-convex lenscomponent 42 and the lens component 43 are interrupted as shown in FIG.16, there occurs no practical problem.

It is of course that the projection optical system as shown in FIG. 15or in FIG. 16 may be constructed in an inverted arrangement in therelationship between the object side and the image side.

In order to obtain the erect image, the above-described projectionoptical system shown in FIG. 16 employed the two reflective surfaces 44a, 44 b having the same function as the pentagonal prism, but insteadthereof the reflective surface for changing the optical path backwardcomposed of two reflective surfaces may be employed, as shown in FIG.17. In FIG. 17, the arrangement is different from the projection opticalsystem in FIG. 16 in that the reflective surface 41 b for changing theoptical path backward is replaced by two reflective surfaces 51 b, 51 cconstituting a dach surface having a ridge line along the Y direction(the direction normal to the drawing plane) and the two reflectivesurfaces 44 a, 44 b are replaced by a reflective surface 54 a inclinedat 45° relative to the surface of plate 9. In FIG. 17, a plano-convexlens component 52 and a lens component 53 having a reflective surface 53a have the same functions as those of the plano-convex lens component 42and the lens component 43 in FIG. 16, respectively.

In FIG. 17, the light from the mask 8 is deflected 90° in optical pathby a semi-reflective surface 51 a and then passes through theplano-convex lens component 52 and the lens component 53 to reach thereflective surfaces 51 b, 51 c, forming a primary image of mask 8 there.The primary image is inverted upside down by the reflective surfaces 51b, 51 c and again passes through the plano-convex lens component 52 andthe lens component 53 then to pass through the semi-reflective surface51 a. The light passing through the semi-reflective surface 51 a isdeflected 90° in optical path by the reflective surface 54 a to go outof a reflecting member 54, forming a secondary image of mask 8. Here,the secondary image is a real-size erect image.

In case that the projection optical system forms no intermediate image(primary image) as shown in FIG. 15 or in case that the optical systemdoes not allow a field stop to be placed at theintermediate-image-formed position as shown in FIG. 17, the shape ofillumination region by the illumination optical system may be arrangedas similar to the shape of a desired field region. For example, if theapertures 107 a, 107 b in the field stop 107 in the illumination opticalsystem of FIG. 4 are shaped in a trapezoid profile, trapezoidillumination regions can be obtained.

Since the projection optical systems in FIGS. 15-17 are equipped with nofield stop, the field regions on the mask 8 must be precisely defined bythe illumination optical system 10. However, the projection opticalsystems in FIGS. 15-17 each is composed of a Dyson optical system, whichcan achieve excellent imaging performance with little occurrence ofoptical aberrations, as compared with the projection optical systemcomposed of two Dyson partial optical systems as shown in FIG. 6.

As described above, in the exposure apparatus of the present embodimenta plurality of projection optical systems form an exposure region havinga wide width in the direction perpendicular to the scanning direction,so that the exposure region can be formed in a large scale withoutincreasing the scale of the projection optical systems. In the presentembodiment each projection optical system is compact in scale, which canprevent an increase in aberrations due to proportional enlargement andwhich can permit scanning exposure with excellent imaging performance.

The second embodiment of the present invention is next describedreferring to the accompanying drawings.

FIG. 18 is a perspective view to show the structure of an exposureapparatus according to the second embodiment of the present invention.Also, FIG. 19 is a drawing to show the structure of projection opticalsystems in the exposure apparatus of FIG. 18.

The second embodiment is different from the embodiment as shown in FIG.3 in that the structure of projection optical systems 302 a-302 g isdifferent from that in the first embodiment as detailed below and inthat because of it the shape of field regions 308 a-308 g and exposureregions 309 a-309 g is substantially of a semi-circular ring. The secondshown in FIG. 18 is the same as the first embodiment shown in FIG. 3except for the above points.

FIG. 19 is a drawing to schematically show the structure of eachprojection optical system. A projection optical system as shown iscomposed of a first partial optical system 321-323, a field stop 324,and a second partial optical system 325-327. Each of the first partialoptical system 321-323 and the second partial optical system 325-327 isan Offner optical system and is constructed in the same structure.

The first partial optical system is composed of an isosceles trapezoidprism 321 having a first reflective surface 321 a for deflecting lightfrom the mask 8 in the X-axis direction (to the right in the drawing), aconcave mirror 322 for reflecting light reflected by the firstreflective surface 321 a of isosceles trapezoid prism 321 to the left inthe drawing, and a convex mirror 323 disposed as opposed to the concavemirror 322 with the axis common to the optical axis of concave mirror322. As described above, the second partial optical system hascompletely the same structure as that of the first partial opticalsystem. In FIG. 19, constituent elements in the second partial opticalsystem are denoted by reference numerals different from those in thefirst partial optical system, but redundant description will be omittedas to the structure of the second partial optical system.

Illumination light passing through the mask 8 is deflected to the rightin the drawing by the first reflective surface 321 a of the isoscelestrapezoid prism 321 to impinge on the concave mirror 322. The lightreflected to the left in the drawing by the concave mirror 322 is thenreflected to the right in the drawing by the convex mirror 323 again toimpinge on the concave mirror 322. The light again reflected to the leftin the drawing by the concave mirror 322 is then deflected downward inthe drawing by the second reflective surface 321 b of the isoscelestrapezoid prism 321 to form a primary image of a pattern of mask 8between the first partial optical system and the second partial opticalsystem.

The thus formed primary image by the first partial optical system321-323 is a real-size image of mask 8 for which the lateralmagnification is positive in the X direction and negative in the Ydirection. A field stop 324 is placed at the position where the primaryimage is formed.

The light from the primary image passing through the field stop 321 isdeflected to the right in the drawing by a first reflective surface 325a of the isosceles trapezoid prism 325 to impinge on a concave mirror326. The light reflected to the left in the drawing by the concavemirror 326 is then reflected to the right in the drawing by a convexmirror 327 again to impinge on the concave mirror 326. The light againreflected to the left in the drawing by the concave mirror 326 isdeflected downward in the drawing by a second reflective surface 325 bof the isosceles trapezoid prism 325 to form a secondary image of apattern of mask 8 on the plate 9.

The second partial optical system has the same structure as the firstpartial optical system, as described above, so that the second partialoptical system forms a real-size image of the primary image for whichthe lateral magnification is positive in the X direction and negative inthe Y direction. Accordingly, the secondary image formed on the plate 9through the first and second partial optical systems is a real-sizeerect image (an image with positive lateral magnifications in the Xdirection and in the Y direction) of mask 8. The projection opticalsystems each composed of the first and second Offner partial opticalsystems are both side (both object side and image side) telecentricoptical systems.

The projection optical system in FIG. 19 is so arranged that the concavemirror 322 in the first partial optical system and the concave mirror326 in the second partial optical system both are directed to the leftin the drawing, whereby the size of projection optical system can bedecreased and in turn the exposure apparatus can be made compact inscale.

Also, the optical axes of projection optical systems 302 a-302 d and theoptical axes of projection optical systems 302 e-302 g are parallel tothe X axis and the apparatus is so arranged that the isosceles trapezoidprisms in the projection optical systems. 302 a-302 d and the isoscelestrapezoid prisms in the projection optical systems 302 e-302 g arelocated close to each other, that is, that the first group of projectionoptical systems 302 a-302 d are opposed to the second group ofprojection optical systems 302 e-302 g.

FIGS. 20 and 21 are drawings to show a first example of shape of anaperture in the field stop 324. FIG. 20 shows an aperture 324A formed inthe field stop 324 and FIG. 21 shows a relation between the shape ofaperture 324A and a maximum field region.

As shown by the dashed line in FIG. 21, a maximum field region asdefined as a region with sufficiently small aberrations is nearlysemi-annular or half-ring in the Offner optical system. Accordingly, theshape of aperture 324A formed in the field stop 324 is defined in theabove semi-annular maximum field region.

In FIG. 21, the length of aperture 324A is shown as 324M in thedirection (corresponding to the horizontal direction in the drawing)perpendicular to the scanning direction, and within 324M the width inthe scanning direction (corresponding to the vertical direction in thedrawing) is arranged to be constant (324W) in a central opening portion324 a defined by two arcs 324 c and 324 d within the length of 324L. Inorder to maximize the scanning speed, the width 324W of the centeropening portion 324 a in the scanning direction is preferably selectedas to take a maximum area with respect to the maximum field region.

On the other hand, end opening portions 324 b (as hatched in thedrawing) other than the center opening portion 324 a with the length324L are triangular so that the width in the scanning direction linearlydecreases toward the end.

FIGS. 22 and 23 are drawings to show a second example of shape of anaperture in the field stop 324. FIG. 22 shows an aperture 324B formed inthe field stop and FIG. 23 shows a relation between the shape ofaperture 324B and a maximum field region.

In FIG. 23, the length of aperture 324B is shown as 324M in thedirection (corresponding to the horizontal direction in the drawing)perpendicular to the scanning direction, and within 324M the width inthe scanning direction (corresponding to the vertical direction in thedrawing) is arranged to be constant (324w) in a center opening portion324 a as defined by two polygonal lines 324 c and 324 d in the length of324L. In order to maximize the scanning speed, the width 324W of thecenter opening portion 324 a in the scanning direction is preferablyselected as to become maximum with respect to the maximum field region.

On the other hand, end opening portions 324 b (as hatched in thedrawing) other than the center opening portion 324 a with the length324L are shaped triangular so that the width in the scanning directionlinearly decreases toward the end.

A basic difference between the above two examples is that the centeropening portion 324 a is defined by the two arcs in the aperture in thefield stop shown in FIGS. 20 and 21 while the center opening portion 324a is defined by the two polygonal lines in the aperture in the fieldstop shown in FIGS. 22 and 23.

FIG. 24 is a drawing to show a layout of field stops on the mask,showing a planar positional relation between field stops 308 a-308 gdefined by the projection optical systems 302 a-302 g and the mask 8.

In FIG. 24, a rectangular circuit pattern PA is formed on the mask 8 anda light-shielding portion LSA is provided to surround the circuitpattern PA. The illumination optical system 10 illuminates illuminationregions 311 a-311 g surrounded at least by the dashed lines in thedrawing with almost uniform illuminance.

The field stops in associated projection optical systems 302 a-302 gmake the field regions 308 a-308 g defined in a shape of crescent moonas shown by the hatched portions in the drawing enclosed in theillumination regions 311 a-311 g.

Here, convex sides of the field regions 308 a-308 d are arranged to beopposed to those of the field regions 308 e-308 g, and the triangularends of field regions overlap with the opposed triangular ends ofadjacent field regions in the X direction (scanning direction).

The reason why the first group of field regions 308 a-308 d and thesecond group of field regions 308 e-308 g are alternately arranged inthe Y direction is that because of each projection optical system beinga both side telecentric optical system the regions occupied by theprojection optical systems 302 a-302 g on the XY plane are larger thanthe corresponding field regions 308 a-308 g.

Namely, if only linearly aligned projection optical systems 302 a-302 dare used to define the field regions 308 a-308 d by field stops thereof,there appear spacings between the regions in the Y direction.Consequently, a continuous exposure region in the Y direction cannot besecured on the plate 9 only by the projection optical systems 302 a-302d. Then the projection optical systems 302 e-302 g are added tocomplement the Y-directional spacings among the field regions 308 a-308d by corresponding field regions 308 e-308 g, securing a continuousexposure region in the Y direction.

The field regions 308 a and 308 d are positioned such that in the centerportion as the region with constant width in the scanning direction theyintersect with the border between the light-shielding portion LSA andthe circuit pattern PA.

As described above, even with the Offner projection optical systemsbeing used, the field regions 308 a-308 g on the mask 8 are so arrangedthat a sum of lengths of field regions along the scanning direction (Xdirection) is constant at an arbitrary position in the direction (Ydirection) perpendicular to the scanning direction, similarly in case ofthe Dyson projection optical systems being used. Namely, in the exposureregions 309 a-309 g which are real-size erect images of the fieldregions, the sum of lengths of field regions along the scanningdirection (x direction) also becomes constant at an arbitrary positionin the direction (Y direction) perpendicular to the scanning direction.As a result, scanning exposure can provide a uniform exposuredistribution over the entire surface on the plate 9.

FIG. 25 is a drawing to show the structure of another projection opticalsystem.

The projection optical system of FIG. 25 is basically different from theprojection optical system of FIG. 19 composed of two Offner partialoptical systems and a field stop in that it includes one Offner opticalsystem and excludes the field stop.

Further, the projection optical system of FIG. 25 is the same instructure as each partial optical system in FIG. 19 but is different inthat the first reflective surface of isosceles trapezoid prism is a dach(roof) surface.

In the projection optical system of FIG. 25, illumination light passingthrough the mask 8 is deflected to the right in the drawing by a dachsurface 351 a of an isosceles trapezoid prism 351 to impinge on aconcave mirror 352. The light reflected to the left in the drawing bythe concave mirror 352 is reflected to the right in the drawing by aconvex mirror 353 again to impinge on the concave mirror 352. The lightagain reflected to the left in the drawing by the concave mirror 352 isdeflected downward in the drawing by a reflective surface 351 b of theisosceles trapezoid prism 351 to form a real-size erect image of apattern of mask 8 on the plate 9.

Thus, the dach surface 351 a inverts the image orientation in thedirection (the direction perpendicular to the drawing plane or the Ydirection) perpendicular to the optical axis in the object plane and inthe image plane. Then an erect image of the pattern on the mask 8 isformed on the plate 9 such that the lateral magnification is positiveboth in the direction along the optical axis (in the X direction) and inthe direction perpendicular to the optical axis (in the Y direction) inthe object plane and in the image plane. Accordingly, such a scanningexposure apparatus having a plurality of projection optical systems canbe so arranged that the scanning direction of mask 8 is made coincidentwith the scanning direction of plate 9.

Next described referring to FIG. 26 is a preferable layout of projectionoptical systems in the second embodiment. FIG. 26 is an XY plan view toshow a relation between two sets of projection optical systems and fieldregions (exposure regions). In FIG. 26, members having the samefunctions as those in the first embodiment are denoted by the samereference numerals.

In FIG. 26, a projection optical system 302 a for Forming an image offield region 308 a on the object plane (mask surface in the embodiment)is illustrated only with an isosceles trapezoid prism 321A, a concavemirror 322A and a convex mirror 323A, and a projection optical system302 b for forming an image of field region 308 b on the object planeonly with an isosceles trapezoid prism 321B, a concave mirror 322B and aconvex mirror 323B. Here, let 324L be an inside (arc center side)Y-directional length in the arcuate field region and 324M be aY-directional maximum length of field region. Then the distance d in theY direction between the optical axis A_(xa) of projection optical system302 a and the optical axis A_(xb) of projection optical system 302 b ispreferably determined to satisfy the following relation:

d=324 L+(324 M−324 L)/2  (5)

If the two sets of projection optical systems 302 a, 302 b do notsatisfy the above conditional formula (5), the field regions do notoverlap with each other on the object plane or the X-directional(scanning direction) width of field regions cannot be constant, which isnot preferable.

The conditional formula (5) holds if the above 324L and 324M are not thelengths in the field regions on the object plane but the lengths in theexposure regions on the image plane (the plate surface in theembodiment) or the lengths in the field stops.

Also, the above conditional formula (5) can be applied to cases wherethree or more projection optical systems are arranged or to cases thatthe projection optical systems are of the Dyson type. In case theprojection optical systems are of the Dyson type, and if the fields ofthe Dyson optical systems are trapezoid, 324L may be assigned to thelength of shorter edge and 324M to the length of longer edge out of apair of parallel edges in each trapezoid field.

Next the third embodiment of a projection optical system will beexplained below, referring to FIGS. 27-28. FIG. 27 shows a structure ofthe third embodiment. A first projection optical system 535 a shown inFIG. 27 corresponds to the projection optical system 2 a shown in FIG. 6and the mask 8, the glass plate 9 and the arrangement thereof are thesame as those shown in FIG. 6.

In FIG. 27, the first projection optical system 535 a has a firstpartial optical system K1 for forming a primary image of a circuitpattern on the mask 8, and a second partial optical system K2 or formingan erect image (secondary image) of the circuit pattern on the plate 9,based on light from the primary image. The first partial optical systemK1 has a right-angle prism P1 with reflective surfaces P1 a, P1 binclined at 45° to the surface of mask 8 (XY plane), a refractiveoptical system G1 of a positive refractive power as a whole having apositive lens group L11, a negative lens group L12, and a positive lensgroup L13, and a plane reflective surface M1.

Also, the second partial optical system K2 has a right-angle prism P2with reflective surfaces P2 a, P2 b inclined at 45° to the surface ofplate 9 (XY plane), a refractive optical system G2 of a positiverefractive power as a whole having a lens group L21 of a positiverefractive power, a lens group L22 of a negative refractive power, and alens group L23 of a positive refractive power, and a plane reflectivesurface M2. Here, a field stop FS is provided at a position where theprimary image of the circuit pattern is formed by the first partialoptical system K1.

The circuit pattern on the mask 8 is illuminated under nearly uniformilluminance by the illumination optical system 10, and light through thecircuit pattern is deflected 90° by the reflective surface P1 a of theright-angle prism P1 to advance through the positive lens group L11,negative lens group L12, and positive lens group L13 in the named orderto reach the plane reflective surface M1. Here, the plane reflectivesurface M1 is located substantially at the rear focal-point position ofthe refractive optical system G1 composed of the positive lens groupL11, negative lens group L12, and positive lens group L13. Namely, theplane reflective surface M1 is located on the pupil plane of the firstpartial optical system K1. The rear focal-point position of therefractive optical system G1 is a position of the rear focal point whenthe side of the right-angle prism P1 is defined as the front side andthe side of the plane reflective surface M1 is the rear side.

Next, the light reflected by the plane reflective surface M1 travelsthrough the positive lens group L13, negative lens group L12, andpositive lens group L11 toward the reflective surface P1 b of theright-angle prism P1. Here, the refractive power exerted on the lightbeam incident into the positive lens group L11 and then emergent towardthe plane reflective surface M1 is approximately equal to that exertedon the light beam incident from the plane reflective surface M1 into thelens group L13 and then emergent from the positive lens group L11.

Then the light reaching the reflective surface P1 b of the right-angleprism P1 is deflected approximately 90° by the reflective surface P1 bto form the primary image of the circuit pattern at the position of thefield stop FS. For the primary image, the lateral magnification in the Xdirection is approximately +1 and the lateral magnification in the Ydirection is approximately −1.

The light from the primary image travels through the second partialoptical system K2 to form the secondary image of the circuit pattern onthe plate 9. Here, the lateral magnifications of the secondary image inthe X direction and the Y direction are nearly +1. Namely, the secondaryimage formed on the plate 9 is an erect image. Since the second partialoptical system K2 has the same function as the first partial opticalsystem K1 does, the detailed description thereof is omitted herein.

Accordingly, as explained in the first embodiment, an image formed onthe plate 9 is a real size erect image of a circuit pattern on the mask8, a scanning exposure can be performed by moving integrally the both ofthe mask 8 and the plate 9.

In addition, since the plane reflective surface M1 is located at therear focal-point position of the refractive optical system G1, the firstpartial optical system K1 as described above is telecentric on the sideof mask 8 and on the side of field stop FS. Further, since the planereflective mirror M2 is located at the rear focal-point position of therefractive optical system G2, the second partial optical system K2 isalso telecentric on the side of field stop FS and the side of plate 9.Accordingly, the first projection optical system 535 a is a both side(mask 8 side and plate 9 side) telecentric optical system.

Next, the exposure area of the first projection optical system 535 a inFIG. 27 is described referring to FIGS. 28A-28C. FIG. 28A is a plan viewto show a relation between an effective field region and the field ofthe first Projection optical system 535 a in the XY plane on the mask 8,FIG. 28B is a plan view of the field stop FS, and FIG. 28C is a planview to show a relation between the effective exposure region and theexposure region of the first projection optical system 535 a.

In FIG. 28A, the effective field region, which is a maximum field regionobtainable by the first projection optical system 535 a, is asemi-circular region surrounded by the dashed line on the mask 8. Here,if the shape of the aperture portion FSa in the field stop FS istrapezoid as shown in FIG. 28B, the field region 8 a of the firstprojection optical system 535 a on the mask 8 is trapezoid as similar tothe shape of the aperture portion FSa. It is needless to mention thatthis field region 8 a is included in the effective field region.

Also, as shown in FIG. 28C, the effective exposure region, which is themaximum exposure region obtainable by the first projection opticalsystem 535 a on the plate 9, is a semi-circular region surrounded by thedashed line. Here, the aperture portion FSa of the field stop FS definesthe exposure region 9 a on the plate 9 in a trapezoid shape similar tothe aperture portion FSa. This exposure region 9 a is also included inthe effective exposure region. In this arrangement of the trapezoidexposure region 9 a, the height of the trapezoid in the X direction isthe slit width, and hypotenuse portions (portions changing their heightsin the X direction) at the Y-directional end portions are overlapregions (regions overlapping in the Y direction with adjacent exposureregions when a plurality of projection optical systems are arranged).The total structure and the scanning method etc. except for the concretestructure of the projection optical system 535 a is the same as those ofthe first embodiment and therefore, the detail explanation thereto isomitted.

Next, the forth embodiment of the projection optical system will beexplained below.

The forth embodiment is shown in FIG. 29.

As shown in FIG. 29, in the forth embodiment, the first projectionoptical system has a right-angle prism 511 with reflective surfaces 511a, 511 b inclined at 45° to the surface of mask 8 (XY plane), arefractive optical system 536 having a positive refractive power as awhole, and a reflective member 537 disposed at the rear focal-pointposition of the refractive optical system 536. Here, the refractiveoptical system 536 has the same function as the refractive opticalsystem G1 in the first projection optical system shown in FIG. 27.Further, the reflective member 537 has right-angle roof reflectivesurfaces 537 a, 537 b with a ridgeline along the Z direction, and theridgeline is located so as to be coincident with the rear focal-pointposition of the refractive optical system 536.

The light from the mask 8 illuminated by the illumination optical system10 is deflected 90° by the reflective surface 511 a to enter therefractive optical system 536. The light passing through the refractiveoptical system 536 is reflected twice by the right-angle roof reflectivesurfaces 537 a, 537 b of the reflective member 537 to be incident againinto the refractive optical system 536. The light from the right-angleroof reflective surfaces 537 a, 537 b and through the refractive opticalsystem 536 is deflected 90° by the reflective surface 511 b of theright-angle prism 511, and thereafter impinges on the plate 9. Since theright-angle root reflective surfaces 537 a, 537 b invert the orientationof image in the Y direction, a real-size erect image of mask 8 is formedon the plate 9. Since the reflective member 537 is located at the rearfocal-point position of the refractive optical system 536, the firstprojection optical system is a both side telecentric optical system.

The forth embodiment is so arranged that the right-angle roof reflectivesurfaces 537 a, 537 b are located at the rear focal-point position ofthe refractive optical system 536, but such roof reflective surfaces maybe provided in a reflective surface for deflecting an optical path.

Next the fifth embodiment is shown in FIG. 30.

Only the first projection optical system in the projection opticalsystem is shown also in FIG. 30.

As shown in FIG. 30, the first projection optical system has areflective surface 512 inclined at 45° to the surface of mask 8 (XYplane), a refractive optical system 536 of a positive refractive poweras a whole, a plane reflective mirror 538 disposed at the rearfocal-point position of the refractive optical system, and a reflectivemember 513 having the roof reflective surfaces. Since the refractiveoptical system 536 is the same as the refractive optical system of theforth embodiment shown in FIG. 29 is omitted herein.

The reflective member 513 has two reflective surfaces (roof reflectivesurfaces) 513 a, 513 b perpendicular to each other, for example as shownin FIG. 31. Here, a ridgeline 513 c of the two reflective surfaces 513a, 513 b has an inclination of 45° relative to the XY plane.

Returning to FIG. 30, the light from the mask 8 is deflected 90° by thereflective surface 512 to travel through the refractive optical system536 and then to reach the plane reflective surface 538. The lightreflected by the plane reflective surface 538 passes again through therefractive optical system 536 to reach the reflective member 513. Thelight reaching the reflective member 513 is deflected 90° toward theplate 9 and also is inverted left to right in the Y direction.Accordingly, a real-size erect image of mask 8 is formed on the plate 9.

In the fifth embodiment shown in FIG. 30, the roof reflective surfacesare present in the optical path between the refractive optical system536 and the plate 9. The roof reflective surfaces may be arranged in theoptical path between the mask 8 and the refractive optical system.Considering negative influence due to errors of the roof reflectivesurfaces, the roof reflective surfaces are preferably set near the plate9.

The reflective member 513 is composed of the plane surface reflectivemirrors in the modification of FIG. 30, but it may be constructed of aright-angle roof prism.

In the forth and fifth embodiments shown in FIG. 29 and FIG. 30, thefield stop cannot be disposed in the optical path of the projectionoptical system. In such cases, the field stop may be disposed in theoptical path of the illumination optical system.

Also, the fifth and forth embodiments showed the trapezoid exposureregions, but the shape of exposure region is not limited to trapezoid.For example, as shown in FIGS. 32A, 32B, and 32C, the exposure regionmay be arcuate. FIG. 32A is a plan view to show a relation between theeffective field region and the arcuate field of the first projectionoptical system in the XY plane on the mask 8, FIG. 32B is a plan view ofa field stop with an arcuate aperture portion, and FIG. 32C is a planview to show a relation between the effective exposure region and thearcuate exposure region of the first projection optical system.

In FIG. 32A, the effective field region of the first projection opticalsystem (the maximum field region obtainable by the first projectionoptical system) is a semi-circular region surrounded by the dashed lineon the mask 8. Here, if the shape of the aperture portion in the fieldstop is arcuate as shown in FIG. 32B, the field region of the firstprojection optical system on the mask 8 is of an arc similar to theshape of the aperture portion. This arc includes two contours ofcircular parts with different centers of curvature in the X directionbut with a same radius of curvature, and contours of right-angletriangle parts in the Y-directional end portions. As shown in FIG. 32C,the effective exposure region of the first projection optical system onthe plate 9 (the maximum exposure region obtainable by the firstprojection optical system) is a semi-circular region surrounded by thedashed line. Here, the arcuate aperture portion in the field stopdefines the exposure region on the plate 9 in an arcuate shape similarto the aperture portion. This arcuate exposure region is within theeffective exposure region of the first projection optical system. Inthis arrangement of the arcuate exposure region, the spacing in the Xdirection between the centers of curvature of the contours of circularparts is the slit width, and the portions of right-angle triangularcontours are overlap regions (regions overlapping in the Y directionwith exposure regions of adjacent second projection optical systems).

When the arcuate exposure region is employed as shown in FIGS. 32A, 32B,and 32C, portions with a nearly constant image height are used in theprojection optical system. In that case, a requirement is that theprojection optical system is corrected for aberration at a specificimage height, which enjoys an advantage of simplifying the opticaldesigning.

In the above-described embodiments the refractive powers of the lensgroups in the refractive optical system are arranged so as to bepositive, negative, and positive in this order. It is, however, needlessto mention that the arrangement of refractive powers in the refractiveoptical system is not limited to this arrangement.

In the third, forth and fifth embodiments, the first and second partialoptical systems may be replaced by the Offner optical system or theDyson optical system. However, the partial optical systems of thepresent invention may have a smaller diameter of optical system than theOffner optical system, and may have a longer working distance than theDyson optical system.

In the above third, forth and fifth embodiments, as similar to thedescribed in the first and second embodiments, they can also provide theexposure apparatus which can perform projection exposure under excellentoptical performance without a decrease in throughput even for a largeexposure region.

Next the sixth embodiment of the projection optical system will beexplained below, referring to FIGS. 33-38D. The combination ofprojection optical systems 630 and 640 shown in FIG. 33 corresponds tothe projection optical system 2 a of the first embodiment. The mask 8,the plate 9 and the other except for the projection optical system arethe same as those of the first embodiment.

In FIG. 33, the mask 8 is placed so that the circuit pattern thereoffaces down in the drawing (to the projection optical system). Further, apellicle film 611 for preventing a trouble due to attachment of dust tothe circuit pattern is provided on the circuit pattern side of the mask8.

The projection optical system of FIG. 33 has a first image-formingoptical system 630 for forming a primary image of mask 8, a field stopFS disposed at a position of the primary image, and a secondimage-forming optical system 640 for forming a secondary image of mask 8on the plate 9, based on light from the primary image, wherein the firstimage-forming optical system 630 is constructed of an Offner opticalsystem OF and the second image-forming optical system 640 of a Dysonoptical system DY. Here, the Offner optical system OF has a trapezoidmirror 631 with two reflective surfaces inclined relative to the XYplane (mask surface), a concave mirror 632, and a convex mirror 633.Further, the Dyson optical system DY has a prism 641 having a totallyreflective surface inclined relative to the XY plane (plate surface), aplano-convex lens component 642, a concave mirror 643, and a prism 644having a totally reflective surface inclined relative to the XY plane.

Light from the mask 8 illuminated is deflected about 90° by onereflective surface of the trapezoid mirror 631, thereafter travels viathe concave mirror 632 and convex mirror 633 in this order, is againreflected by the concave mirror 632, and then reaches the otherreflective surface of the trapezoid mirror 631. The light reaching thisreflective surface is deflected about 90°, and thereafter reaches theaperture portion in the field stop FS to form an intermediate image ofmask 8 there. Here, the intermediate image of mask 8 is an image withthe lateral magnification in the X direction being +1 and the lateralmagnification in the Y direction being −1.

The light from the intermediate image formed on the field stop FS isdeflected about 90° in optical path thereof by the prism 641, thereaftertravels via the plano-convex lens component 642, the concave mirror 643,and the plano-convex lens component 642 in the named order to reach theprism 644, and is deflected about 90° in optical path thereof by theprism 644 to form an image of the intermediate image (secondary image ofmask 8). Here, the image of the intermediate image is an image with thelateral magnification in the X direction being +1 and the lateralmagnification in the Y direction being −1 with respect to theintermediate image. Namely, the secondary image on the plate 9 is areal-size erect image with both the lateral magnifications in the Xdirection and the Y direction being +1 with respect to the mask 8.

Here in the sixth embodiment, the Offner optical system OF is arrangedas the first image-forming optical system 630 on the mask 8 side, whilethe Dyson optical system DY as the second image-forming optical system640 on the plate 9 side. The reason is as follows. In recent years,there are many cases where the pellicle film is provided on the circuitpattern side of mask 8 as shown in FIG. 33. In such cases, the workingdistance to the mask 8 needs to be extended. However, the Dyson opticalsystem generally has a property that spherical aberration becomesuncorrectable with an extended working distance. Here, the workingdistance could be extended if refractive indices of the prisms 641, 644should be made larger than that of the plano-convex lens component 642.This technique, however, can earn only a working distance of several mm.There are some cases where a magnification adjusting optical system oran image position correcting optical system as described below isprovided in the projection optical system. Thus, if the working distanceof the projection optical system itself is short, it becomes difficultto dispose such a magnification adjusting optical system or imageposition correcting optical system therein.

Thus, the sixth embodiment employs the Offner optical system OF with along working distance on the mask 8 side. This is effective for the mask8 with the pellicle film 611. Further, because the spacing between theOffner optical system OF and the intermediate-image-formed position (theposition of field stop) is extended, there is an advantage that themagnification adjusting optical system and the image position correctingoptical system can be disposed at this position.

The above magnification adjusting optical system is next describedreferring to FIG. 33. As shown in FIG. 33, the sixth embodiment is soarranged that a magnification adjusting optical system consisting of aplano-convex lens 651 and a plano-concave lens 652 is disposed in theoptical path between the Offner optical system 630(OF) and the Dysonoptical system 640(DY). These plano-convex lens 651 and plano-concavelens 652 each are arranged so as to be movable along the optical axis(or in the Z-axis direction in this case). Here, moving the plano-convexlens 651 and plano-concave lens 652 in the optical-axis direction, thelateral magnification changes for the intermediate image of mask 8formed on the field stop FS. Accordingly, it becomes possible to changethe projection magnification of the entire projection optical systemcomposed of the Offner optical system 630(OF) and the Dyson opticalsystem 640(DY).

In the sixth embodiment, at least three set of the combination of theOffner optical system and the Dyson optical system are provide and eachof the Offner optical systems forms intermidiate image of illuminationregion in the mask 9 in and each of the Dyson optical system forms animage (which is secondary image of the illumination region) of theintermidiate images on exposure regions 9 a 9 b or 9 c on the plate 9.The secondary image is an real-erect image of the illumination region.

As shown in FIG. 34, exposure regions 9 a-9 c on the plate 9 areadjacent to each other as overlapping by a predetermined amount in the Ydirection. Here, overlapping regions between the respective exposureregions 9 a-9 c are called as overlap regions. In an overlap region, asum of X-directional lengths (slit widths) of the exposure regions 9 a,9 c is determined so as to be always constant at any position in the Ydirection. Similarly, a sum of X-directional lengths (slit widths) ofthe exposure regions 9 b, 9 c is determined so as to be always constantat any position in the Y direction. Accordingly when the exposure isperformed while the mask 9 and the plate is moved integrally along to adirection X shown in FIG. 33, as similar to the first embodiment, all ofcircuit patterns on the mask 8 is seauencially transferred on the plate9.

Next described referring to FIGS. 35A-35D is the exposure regionobtainable by the projection optical system according to the sixthembodiment. FIG. 35A is a drawing to show a developed state of opticalpaths in the projection optical system. The Offner optical system OF andthe Dyson optical system DY shown in FIG. 35A have a common optical axisAx. In the sixth embodiment, “to have a common optical axis Ax” meansthat image heights of principal rays of light beams traveling from theOffner optical system OF to the Dyson optical system DY (or light beamstraveling from the Dyson optical system DY to the Offner optical systemOF) are equal to each other.

Here, the maximum field that can be achieved by the Offner opticalsystem OF is semi-circular, as shown in FIG. 35B, because the lightbeams are eclipsed by the convex mirror 633. Also, the Offner opticalsystem has astigmatism, and the slit width d is determined by a regionof image heights little affected by the astigmatism. The maximum fieldthat can be achieved by the Dyson optical system DY is semi-circular asshown in FIG. 35C. Thus, the field of the entire projection opticalsystem is determined by the field of the Offner optical system if thefield of the Dyson optical system covers the field of the Offner opticalsystem. In other words, in the case where the maximum image height YDYof the Dyson optical system DY is larger than the maximum image heightYOF of the Offner optical system OF (or if YOF≦YDY), the field of theOffner optical system OF is the field of the entire projection opticalsystem. FIG. 35D shows the field of the entire projection opticalsystem.

In scanning exposure it is required that the length in the scanningdirection, of the exposure region for scanning the plate (the slit widthof the exposure region) is always constant at any position in thedirection perpendicular to the scanning direction in order to keepexposure amounts constant in the direction perpendicular to the scanningdirection. Accordingly, the shape of the exposure region formed on theplate should be an arcuate shape consisting of two contours of circularparts with centers thereof deviating by the slit width d in the scanningdirection and with a same radius of curvature, as shown in FIG. 35E. Inthis case, the arcuate exposure region should be within the scope of thefield of the entire projection optical system as shown in FIG. 34D.

In the case where scanning exposure is made with the plurality ofexposure regions 9 a-9 c as shown in FIG. 34, the X-directional lengthof each exposure region 9 a-9 c needs to be kept always constant at anyposition in the Y direction, as described previously. In this case, thearcuate exposure region of each projection optical system is preferablyan exposure region, as shown in FIG. 36, having contours consisting oftwo circular parts with centers thereof deviating by the slit width d inthe scanning direction and with a same radius of curvature andtriangular parts added to the Y-directional ends of these circularparts, because a wide exposure area can be secured.

Now, for example in fabricating liquid crystal panels of the activematrix type using the exposure apparatus according to the sixthembodiment, overlapping exposures of plural pattern layers becomenecessary in fabrication steps in order to form the active devices.Here, a process treatment is conducted after pattern exposure for acertain layer, and there are cases where the plate 9 expands orcontracts in this process treatment.

In that case, it is necessary to adjust the projection magnification ofmask 8 in accordance with expansion or contraction of plate 9. In caseof normal exposure apparatus with a single projection optical system,the projection magnification of mask 8 can be adjusted by controllingonly the magnification (lateral magnification) of projection opticalsystem; whereas, in case of exposure apparatus with a plurality ofprojection optical systems as in the sixth embodiment, adjustingmagnifications of individual projection optical systems would result incausing a problem that the plurality of exposure regions 9 a-9 c losemutual overlap or gain excessive overlap on the plate 9. Here, the lossof mutual overlap between the plurality of exposure regions 9 a-9 ccauses a problem of an internal missing region without transferredcircuit pattern extending in the scanning direction (X direction) on theplate 9; the excessive overlap between the plural exposure regions 9 a-9c causes a problem of excessive exposure amount in the excessivelyoverlapping regions, resulting in errors in linewidth of the circuitpattern after developed.

Thus, the sixth embodiment is so arranged that a plane-parallel plate653 as shown in FIG. 33 is further provided as rotatable about theX-axis and Y-axis directions as the image position correcting opticalsystem in the optical path between the first image-forming opticalsystem 630 a-630 c and the second image-forming optical system 640 a-640c. Then, on the occasion of magnification adjustment of the projectionoptical system with the plano-convex lens 651 and plano-concave lens 652as shown in FIG. 33, the plane-parallel plate 653 a-653 c is inclinedabout the X-axis direction so as to adjust the positions of the pluralexposure regions 9 a-9 c in the Y direction.

This enables the circuit pattern to be always well transferred onto theplate 9 even if adjustment of magnification is conducted for eachprojection optical system.

In the case where the magnification of each projection optical system isadjusted by the magnification correcting optical system 651, 652 andwhere the image position correcting optical system 653 a-653 c isadjusted about the X-axis direction as described above, the adjustmentis limited to only the adjustment of projection magnification in theY-axis direction. However, the magnification between the mask 8 and theplate 9 in the scanning direction (X-axis direction) can be changed byinclining the plane-parallel plate 653 a-653 c about the Y-axisdirection in the scanning exposure. Here, the plane-parallel plate 653a-653 c as the image position correcting optical system is preferablyconstructed so as to rotate about the Y axis in correspondence to thescanning speed of the mask 8 and plate 9 carried by unrepresentedstages.

Also, aberrations arising from the Offner optical system OF in itselfcan be reduced by loosening curvatures of the concave mirror 632 andconvex mirror 633 in the Offner optical system OF; in that case, theslit width of the field of the Offner optical system OF in itself can beexpanded. In case of a zigzag arrangement of three or more projectionoptical systems, there is a possibility that projection optical systemsadjacent to each other in the Y direction interfere with each otherespecially if the diameters of the Offner optical systems in theprojection optical systems become larger. In such cases, two projectionoptical systems adjacent to each other in the Y direction may be soarranged, as shown in FIG. 37, that for one projection optical systemthe first image-forming optical system 660 a is the Offner opticalsystem OF and the second image-forming optical system 680 a is the Dysonoptical system DY and that for the other projection optical system,inversely, the first image-forming optical system 660 b is the Dysonoptical system DY and the second image-forming optical system 680 b isthe Offner optical system OF.

In the sixth embodiments shown in FIGS. 33-37, the Offner optical systemOF and Dyson optical system DY composing the projection optical systemare arranged to have the common optical axis Ax as shown in FIG. 35A.Here, the Offner optical system OF and Dyson optical system DY composingthe projection optical system may be constructed in a state that theoptical axes thereof are decentered from each other.

Next described referring to FIGS. 38A-38E are the construction of aprojection optical system in which the optical axis of the Dyson opticalsystem DY is decentered with respect to the Offner optical system OF,and the exposure region that can be achieved thereby. FIG. 38A is adrawing to show a developed state of optical paths in the projectionoptical system. In FIG. 38A, the Offner optical system OF and the Dysonoptical system DY composing the projection optical system are in a statethat the respective optical axes AxOF, AxDY are decentered from eachother. The state that the optical axes AxOF, AxDY are decentered fromeach other means that image heights of principal rays of light beamstraveling from the Offner optical system OF to the Dyson optical systemDY (image heights relative to the optical axis AxOF of the Offneroptical system OF) are different from image heights of principal rays oflight beams traveling from the Dyson optical system DY to the Offneroptical system OF (image heights relative to the optical axis AxDY ofthe Dyson optical system DY).

As shown in FIG. 38B, the maximum field that can be achieved by theOffner optical system OF is semi-circular because the light beams areeclipsed by the convex mirror 633. Also, the Offner optical system hasastigmatism, and the slit width d is determined by the scope of imageheights little affected by the astigmatism. Further, the maximum fieldthat can be achieved by the Dyson optical system DY is semi-circular asshown in FIG. 38C.

FIG. 38D shows the field of the entire projection optical system. Inthis case, the maximum field region obtainable by the projection opticalsystem is an overlap region between the arcuate field of the Offneroptical system OF and the semi-circular field of the Dyson opticalsystem DY as represented by the hatched lines in the drawing.

As described previously, it is required in scanning exposure that thelength in the scanning direction, of the exposure region for scanningthe plate (slit width of the exposure region) is always constant at anyposition in the direction perpendicular to the scanning direction.Accordingly, the shape of the exposure region formed on the plate is anarcuate shape, as shown in FIG. 38E, having contours of two circularparts with centers thereof deviating by the slit width d in the scanningdirection and with a same radius of curvature and triangular parts addedto the Y-directional ends of the circular parts. This arcuate exposureregion is within the range of the field of the entire projection opticalsystem shown in FIG. 38D.

In the case where the optical axes AxOF, AxDY of the Offner opticalsystem OF and the Dyson optical system DY are decentered from eachother, the region 613 shown in FIGS. 38C-38E is a region where no lightbeam passes. Thus, this region 613 may be cut off upon producing theDyson optical system DY. In this case, a cross-sectional profile in thedirection perpendicular to the optical axis AxOF of the lens component642 in the Dyson optical system DY is elliptic. This arrangement permitsthe prisms 641, 644 in the Dyson optical system DY to be constructed ina small size, or to have shorter optical path lengths, which expands thespacing between the lens component 642 or the prism 644 and the plate 9,thus presenting an effect of extending the working distance of the Dysonoptical system DY itself.

It is thus understood that if the working distance of the Dyson opticalsystem DY is very short, it is effective to decenter the optical axesAxOF, AxDY of the Offner optical system OF and the Dyson optical systemDY from each other.

As described above, the exposure apparatus in the sixth embodimentaccording to the present invention includes such advantages that withthe Offner optical system OF used on the mask side, the working distanceon the mask side can be taken long, which is ready for masks with apellicle film or the like attached thereto and whereby the magnificationadjusting optical system and the image position correcting opticalsystem may be set in the optical path.

If the optical path lengths of the prisms 641, 642 in the Dyson opticalsystem DY are set short, the working distance of the Dyson opticalsystem DY can be extended. In this case, glass corresponding to theshortened parts of the optical path length in the prisms 641, 644 may beused for the magnification adjusting optical system and the imageposition correcting optical system.

If the Offner optical system OF and the Dyson optical system DY have thecommon optical axis Ax, the concave mirror 633 in the Offner opticalsystem OF may be replaced by a lens component such as a doublet. In thiscase, reflection on the back face of the lens component is used insteadof reflection by the concave mirror 633, thereby correcting chromaticaberration caused in the Dyson optical system DY. Also, astigmatismcaused in the Offner optical system OF can be corrected by the Dysonoptical system, which enables the slit width to be set relatively large.

In the above sixth embodiment, the merits obtained in the first to fifthembodiments can be also obtained.

Further, because the exposure apparatus according to the sixthembodiment uses the so-called Offner optical system as the firstimage-forming optical system, the working distance can be extendedwithout degrading spherical aberration. Generally, the Offner opticalsystem is corrected for astigmatism only in portions at a specific imageheight. In the sixth embodiment, because the so-called Dyson opticalsystem is used as the second image-forming optical system, astigmatismgenerated by the first image-forming optical system can be corrected,thus expanding the image-height range for excellent image-formingperformance. Namely, the slit width can be fully secured upon scanningexposure.

Next the seventh embodiment of the projection optical system will beexplained below, referring to FIGS. 39 and 40.

FIG. 39 is a plan view to show the seventh embodiment of the projectionoptical system. The directions referred below is the same as those ofthe previous embodiments, and elements except for the projection opticalsystem are the same as those of the first embodiment.

In FIG. 39, provided between the mask 8 and the plate 9 are a lens unit702 and a plane reflective mirror 703 having the optical axis Axparallel to an in-plane direction (YZ direction) of these mask 8 andplate 9. Here, the lens unit 702 has a positive refractive power, andthe plane reflective mirror 703 is disposed at a position of the rearfocal point of the lens unit 702. This arrangement makes rays enteringthe lens unit 702 in parallel with the optical axis Ax emergent from thelens unit 702 in parallel with the optical axis Ax.

On the opposite side of the lens unit 702 to the plane reflective mirror703 there are polarizing beam splitters 7PR1, 7PR2 arranged as the firstand second light splitting means. These polarizing beam splitters 7PR1,7PR2 are constructed in such a structure that a polarization separatingsurface 7R1, 7R2, being a dielectric multilayer film for separatinglight beams with mutually orthogonal polarization directions from eachother, is set on a junction plane in a prism type beam splitter. Here,the polarization separating surfaces 7R1, 7R2 are inclined at ±45°relative to the in-plane direction (YZ direction) of the mask 8 andplate 9.

Two reflective mirrors 7M1, 7M2 with mutually orthogonal reflectivesurfaces are placed as the beam transferring means on the opposite sideto the lens unit 702 with respect to the polarizing beam splitters 7PR1,7PR2. Further, a quarter wave plate 7H1 is provided as the phasechanging member in the optical path between the polarizing beamsplitters 7PR1, 7PR2 and the lens unit 702. Here, an aperture stop AS isprovided near the reflective surface of the plane reflective mirror 703,and a field stop FS having an aperture portion in a predetermined shapeis provided in the optical path between the reflective mirror 7M1 andthe reflective mirror 7M2.

On the opposite side of the projection optical system as described abovewith respect to the mask 8 there is provided an illumination opticalsystem 701 for irradiating linearly polarized light with an oscillationplane in the direction normal to the plane of the drawing (s-polarizedlight with respect to the polarization separating surface 7R1 in thepolarizing beam splitter 7PR1) to a predetermined field region on themask 8.

Now, the s-polarized light from the illumination optical system 701 andthrough the mask 8 advances along the X direction, is reflected by thepolarization separating surface 7R1 in the polarizing beam splitter7PR1, and then is deflected so that the optical path thereof runs alongthe Z direction. This s-polarized light passes through the quarter waveplate 7H1 to be converted into circularly polarized light and thereafterthe circularly polarized light enters the lens unit 702. The circularlypolarized light passing through the lens unit 702 is reflected by theplane reflective mirror 703 and again passes through the lens unit 702and the quarter wave plate 7H1 in this order to be converted intop-polarized light. This p-polarized light advances along the Z directionin the drawing and passes through the polarization separating surface7R2 in the polarizing beam splitter 7PR2. Then the p-polarized light isdeflected 90° in optical path thereof by the reflective mirror 7M1 sothat the optical path thereof runs along the X direction, and nextreaches the field stop FS. At this position, an intermediate image ofmask 8 is formed in the aperture portion of the field stop FS. Thelateral magnifications of the intermediate image are +1 for the Zdirection and −1 for the Y direction.

Next, the p-polarized light from the intermediate image is deflected 90°by the reflective mirror 7M2 to advance along the Z direction and againto enter the polarizing beam splitter 7PR1. This p-polarized lightpasses through the polarizing beam splitter 7PR1, and then is convertedthrough the quarter wave plate 7H1 into circularly polarized light,which enters the lens unit 702. The circularly polarized light enteringthe lens unit 702 is reflected by the plane reflective mirror 703, andthereafter again passes through the lens unit 702 and the quarter waveplate 7H1 to be converted into s-polarized light advancing along the Zdirection. The s-polarized light is then incident into the polarizingbeam splitter 7PR2. This s-polarized light is reflected by thepolarization separating surface 7R2 in the polarizing beam splitter 7PR2to advance along the X direction. Then the s-polarized light passesthrough a magnification correcting optical system M composed of convexand concave lenses finely movable along the X direction to reach theplate 9. An image of the field stop FS is formed on the plate 9 with thelateral magnification in the Z direction being +1 and the lateralmagnification in the Y direction being −1. That is, a real-size erectimage (secondary image) of mask 8 is formed on the plate 9 with theX-directional and Z-directional lateral magnifications both being +1.Accordingly, moving the mask 8 and plate 9 together in the Z direction,the pattern on the mask 8 can be serially transferred onto the plate 9,thus realizing scanning exposure.

The magnification correcting optical system 7M as described above isprovided in order to get ready for expansion or contraction etc. ofsubstrate in various processes. This can change the magnification of theprojection optical system itself in the range of 1 to slight enlargementor reduction.

The exposure operation by the present embodiment is next describedbriefly referring to FIG. 40. FIG. 40 is a plan view to show a relationbetween the plate 9 and the exposure region EF in the presentembodiment. In FIG. 40, the vertical direction in the plane of drawingis the Y direction, the horizontal direction in the plane of drawing isthe Z direction, and the direction normal to the plane of drawing is theX direction. This coordinate system of FIG. 40 corresponds to that ofFIG. 39.

In FIG. 40, the trapezoid exposure region EF is first located at thecorner (at edges in the Y direction and Z direction). Here, moving themask 8 and plate 9 together in the Z direction (scanning direction) withrespect to the exposure region EF, the pattern of mask 8 is transferredto a part of plate 9. Then, the mask 8 and plate 9 are moved in the Ydirection (step direction). On this occasion, an amount of movement inthe step direction may be determined so that an overlap region of thetrapezoid exposure region EF before movement overlaps with that aftermovement. The overlap region in the trapezoid exposure region means anexposure region corresponding to a region where a plurality of exposuresare made on the plate 9 by a plurality of exposure regions or a singleexposure region. For example, breaking a trapezoid into a rectangle andtwo triangles on either side of the rectangle in the Y direction, theregions corresponding to these triangles are overlap regions.

After that, the mask 8 and plate 9 are moved along the Z direction,i.e., in the opposite direction to the first scanning exposure, therebyserially transferring the pattern of mask 8 onto the plate 9. After thissecond scanning exposure, the mask 8 and plate 9 are moved along the Ydirection and third scanning exposure is carried out. In this manner,the present embodiment is so arranged that the moving operation alongthe Z direction (scanning exposure operation) and the moving operationalong the Y direction (step operation) are repeated to transfer thepattern on the entire surface of mask 8 onto the plate 9. This is readyfor a large exposure region without an increase in the size ofprojection optical system.

The shape of the exposure region EF is not limited to trapezoid, but maybe for example hexagonal, slit, or arcuate. That is to say, the shape ofthe exposure regions of the previous embodiments can be also applied tothe seventh embodiments.

The seventh embodiment employed such an arrangement that an exposureamount in the overlap region was made equal to that in the exposureregion other than the overlap region by the shape of the apertureportion in the field stop FS, but a light-reducing filter or a filterwith dot patterns may be provided at the end portions of the apertureportion in the field stop.

In the seventh embodiment, there is a possibility that where there arefabrication errors of the quarter wave plate 7H1 or the polarizing beamsplitter 7PR1, s-polarized light is mixed in the p-polarized lighttraveling from the lens unit 702 to the field stop FS whereby thes-polarized light component reaches the plate 9. There is also apossibility that where there are fabrication errors of the polarizationbeam splitter 7PR2, this polarizing beam splitter 7PR2 reflects thep-polarized light traveling from the lens unit 2 to the field stop FSwhereby the p-polarized light reaches the plate 9.

In such cases, the primary image and secondary image of mask are formedon the plate 9, causing a problem of defects in transfer of pattern onthe mask 8. In this case, it is preferred that a focus correctingoptical system with a predetermined refractive power be provided in theoptical path running from the polarizing beam splitter 7PR2 to thepolarizing beam splitter 7PR1. This focus correcting optical system candifferentiate the position of the primary image of mask from theposition of the secondary image of mask in the X direction, which canmake the influence of the primary image of mask ignorable on the plate9.

On this occasion, the primary image of mask 8 is formed by the lightpassing only the optical system consisting of the lens unit 702 and theplane reflective plate 703 and the magnification correcting opticalsystem M, while the secondary image of mask 8 is formed by the lightpassing the optical system, magnification correcting optical system M,and focus correcting optical system. Accordingly, adjusting therefractive powers of the magnification correcting optical system M andfocus correcting optical system, it becomes possible that while theposition of the primary image is shifted from that of the secondaryimage in the X direction, the magnification of the secondary image isadjusted to 1 or a magnification corresponding to expansion orcontraction of substrate. Also, the magnification correcting opticalsystem M and focus correcting optical system both may be placed in theoptical path running from the polarizing beam splitter 7PR2 to thepolarizing beam splitter 7PR1.

Next, a modification of the seventh embodiment is described referring toFIG. 41. This modification is an example in which the quarter wave plate7H1 as the phase changing member in the present embodiment is replacedby a half wave plate 7H2 provided in the optical path between thepolarizing beam splitter 7PR1 and the lens unit 702. In FIG. 41, memberswith like functions as those in the embodiment of FIG. 39 are denoted bythe same reference numerals, and the same coordinate system as in FIG.39 is employed herein.

In FIG. 41, light from the mask 8 illuminated by linearly polarizedlight in the direction perpendicular to the plane of the drawing(s-polarized light with respect to the polarization separating surfaces7R1, 7R2 in the polarizing beam splitters 7PR1, 7PR2), similarly as inthe first embodiment, is reflected by the polarization separatingsurface 7R1 in the polarizing beam splitter 7PR1, and thereafter passesthrough the half wave plate 7H2 to be converted into p-polarized light.This p-polarized light passes the lens unit 702, plane reflective mirror703, and lens unit 702 in this order, and thereafter passes through thepolarizing beam splitter 7PR2. Then the optical path of the p-polarizedlight is deflected 90° by the reflective mirror 7M1 to reach the fieldstop FS. Here, a primary image of mask 8 is formed in the apertureportion of field stop FS with the Z-directional lateral magnificationbeing +1 and the Y-directional lateral magnification being −1, similarlyas in the present embodiment. The optical path of the p-polarized lightfrom the primary image is deflected 90° by the reflective mirror 7M2,and thereafter the p-polarized light passes through the polarizing beamsplitter 7PR1 and then through the half wave plate 7H2 to be convertedinto s-polarized light. This s-polarized light passes the lens unit 702,plane reflective mirror 703, and lens unit 702 in this order andthereafter is reflected by the polarizing beam splitter 7PR2 to passthrough the magnification correcting optical system M and then to reachthe plate 9. By this, a real-size erect image of mask 8 is formed on theplate 9 with the Y-directional and Z-directional lateral magnificationsboth being +1. In this manner, the half wave plate 7H2 can also beapplied as the phase changing member.

Another modification of the present embodiment is next describedreferring to FIGS. 42A and 42B. The second modification according to thepresent invention is an example in which the quarter wave plate 7H1 asthe phase changing member in the present embodiment is formed integrallywith the plane reflective mirror 703. In FIG. 42A members with likefunctions as those in the present embodiment are denoted by the samereference numerals, and the same coordinate system as in FIG. 39 isemployed.

The second modification shown in FIG. 42A is different from the presentembodiment in that the two polarizing beam splitters 7PR1, 7PR2 are madeintegral with each other and in that a reflective member 7HM3, which isa quarter wave plate on the back face of which a reflective film isvapor-deposited, is located at the rear focal point of the lens unit702. Here, as shown by the hatched lines in FIG. 41B, the reflectivefilm is provided in a partial region of the quarter wave plate, and theshape of the region is circular. Thus, this region of the reflectivefilm corresponds to the aperture portion in the aperture stop AS in thepresent embodiment and the first modification. Here, because thereflective film is provided in the partial region of the quarter waveplate, it is sufficient that the function of the quarter wave plate isachieved only in this region, but the other regions do not have to be anaccurate quarter wave plate.

In FIG. 42A, a polarization separating element 7PR with two polarizationseparating surfaces 7R1, 7R2 is provided in the optical path between thereflective mirrors 7M1, 7M2 as the beam transferring member and the lensunit 702, and these polarization separating surfaces 7R1, 7R2 arearranged as perpendicular to each other.

The optical path in the present modification is next described referringto FIG. 42A. In FIG. 42A, light from the mask 8 illuminated by linearlypolarized light in the direction normal to the plane of drawing(s-polarized light with respect to the polarization separating surfaces7R1, 7R2 in the polarization separating element 7PR), similarly as inthe present embodiment, is reflected by the polarization separatingsurface 7R1 in the polarization separating element 7PR, and then passesthrough the lens unit 702 to reach the reflective member 7HM3. Thep-polarized light reaching the reflective member 7HM3 is converted intocircularly polarized light by the quarter wave plate, and is reflectedby the reflective film vapor-deposited on the back face of the quarterwave plate. After that, the circularly polarized light again passesthrough the quarter wave plate to be converted into s-polarized light,which is emergent therefrom. This s-polarized light again passes throughthe lens unit 702 and then through the polarization separating surface7R2 in the polarization separating member 7PR, and the optical paththereof is deflected 90° by the reflective mirror 7M1 to reach the fieldstop FS. Here, the primary image of mask 8 is formed with theZ-directional lateral magnification being +1 and the Y-directionallateral magnification being −1, similarly as in the above embodiment.The optical path of the p-polarized light from the primary image isdeflected 90° by the reflective mirror 7M2, and thereafter thep-polarized light passes through the polarization separating surface 7R1in the polarization separating element 7PR. Then the p-polarized lightpasses through the lens unit 702 to reach the reflective member 7HM3.The polarized light reaching this reflective member 7HM3 is reflectedthereby so that it is again incident into the lens unit 702 afterconverted into s-polarized light. The s-polarized light from thereflective member 7HM3 through the lens unit 702 is reflected by thepolarization separating surface 7R2 in the polarization separatingelement 7PR, and then passes through the magnification correctingoptical system M to reach the plate 9. By this, a real-size erect imageof mask 8 is formed on the plate 9 with the Y-directional andZ-directional lateral magnifications both being +1. In this manner, thephase changing member having a phase changing function may be integratedwith the reflective surface.

Since the seventh embodiment is so arranged that the quarter wave plateis located near the pupil position of the optical system, the degree ofinfluence of the quarter wave plate on the image-forming performance canbe made lower. In the above-described each of the seventh embodiment andthe modifications thereof, instead of providing the beam transferringmember for transferring the light beam from the polarizing beam splitter7PR2 as the second light splitting means in the direction traversing theoptical axis Ax toward the polarizing beam splitter 7PR as the firstlight splitting means, it is also possible to employ such an arrangementthat the light from the second light splitting means is guided directlyto the first light splitting means along the direction traversing theoptical axis Ax. Such an arrangement is next described referring to FIG.43.

FIG. 43 is a plan view to show a third modification of the seventhembodiment to which the Offner optical system is applied in the presentinvention. In FIG. 43, members with like functions as those in theembodiment of FIG. 39 are denoted by the same reference numerals, andthe same coordinate system as in FIG. 39 is employed.

In FIG. 43, provided between the mask 8 and the plate 9 are a concavemirror 704 and a convex mirror 705 having the optical axis Ax parallelto an in-plane direction (YZ direction) of these mask 8 and plate 9.Here, the convex mirror 705 is arranged so as to be approximatelycoincident with the focal point of the concave mirror 704. An aperturestop AS is provided near the convex mirror 705.

On the opposite side to the concave mirror 704 with respect to theconvex mirror 705 polarizing beam splitters 7PR3, 7PR4 are disposed asthe first and second light splitting means. These polarizing beamsplitters 7PR3, 7PR4 have respective polarization separating surfaces7R3, 7R4 inclined at ±45° relative to the in-plane direction (YZdirection) of the mask 8 and plate 9.

A reflective mirror 7M3 for deflecting the light from the mask 8 by 90°to make it travel in parallel with the optical axis Ax is provided inthe optical path between the polarizing beam splitter 7PR3 and the mask8, and a reflective mirror 7M4 for deflecting the light from thepolarizing beam splitter 7PR4 traveling in parallel with the opticalaxis Ax by 90° to make it travel along the direction normal to the plate9 is provided in the optical path between the polarizing beam splitter7PR4 and the plate 8. Here, the two reflective mirrors 7M3, 7M4 are soarranged that the reflective surfaces thereof are perpendicular to eachother.

Also, a quarter wave plate 7H4 is provided as a phase changing member inthe optical path between the polarizing beam splitters 7PR3, 7PR4 andthe concave mirror 704, and a field stop FS having an aperture portionof a predetermined shape is provided in the optical path between thepolarizing beam splitter 7PR3 and the polarizing beam splitter 7PR4.

In the third modification of the seventh embodiment, there is providedan illumination optical system 701 for irradiating linearly polarizedlight with an oscillation plane in the horizontal direction in the planeof drawing (p-polarized light with respect to the polarizationseparating surface 7R3 in the polarizing beam splitter 7PR3) to apredetermined field region on the mask 8.

Next, the third modification of the seventh embodiment is describedalong the optical path. In FIG. 43, the p-polarized light from theillumination optical system 701 and through the mask 8 travels along theX direction in the drawing to reach the reflective mirror 7M3. Theoptical path of the p-polarized light reflected by the reflective mirror7M3 is deflected 90° to advance along the Z direction, and then passesthrough the polarization separating surface 7R3 in the polarizing beamsplitter 7PR3. Then the p-polarized light passes through the quarterwave plate 7H4 to be converted into circularly polarized light. Thiscircularly polarized light is then reflected by the concave mirror 704,convex mirror 705, and concave mirror 704 in this order to advance alongthe Z direction and then to reach the quarter wave plate 7H4. Thep-polarized light reaching the quarter wave plate 7H4 is converted intos-polarized light by the quarter wave plate 7H4, and the s-polarizedlight is reflected by the polarization separating surface 7R4 in thepolarizing beam splitter 7PR4 to advance along the X direction in thedrawing and then to reach the field stop FS. Here, a primary image ofmask 8 is formed in the aperture portion of field stop FS. The lateralmagnifications of the primary image of mask 8 are +1 for the Z directionand −1 for the Y direction.

Next, the s-polarized light from the primary image is reflected by thepolarization separating surface 7R3 in the polarizing beam splitter 7PR3to advance along the Z direction and to pass through the quarter waveplate 7H4 to be converted into circularly polarized light. Thiscircularly polarized light is reflected by the concave mirror 704,convex mirror 705, and concave mirror 704 in this order, and thereafteradvances along the Z direction to pass through the quarter wave plate7H4. Here, because the light from the concave mirror 704 and through thequarter wave plate 7H4 is p-polarized light, this p-polarized lightpasses through the polarizing beam splitter 7PR4 to advance along the Xdirection and the optical path thereof is deflected 90° by thereflective mirror 7M4 to reach the plate 9. By this, an image of thefield stop FS is formed on the plate 9 with the Z-directional lateralmagnification being +1 and the Y-directional lateral magnification being−1. That is, a real-size erect image (secondary image) of mask 8 isformed on the plate 9 with the Y-directional and Z-directional lateralmagnifications both being +1. Also in the present modification, themagnification correcting optical system 7M consisting of convex andconcave lenses finely movable along the X direction is disposed in theoptical path between the polarizing beam splitter 7PR4 (reflectivemirror 7M4) and the plate.

As described, the third modification of the seventh embodiment can alsorealize scanning exposure by moving the mask 8 and plate 9 together inthe Z direction.

The third modification of the seventh embodiment employs the structurethat the light beam from the second light splitting means is guideddirectly to the first light splitting means without interposition ofbeam transferring member. This arrangement allows use of portions withhigh image heights in the Offner optical system. The third modificationof the seventh modification employs the field stop FS with an arcuateaperture portion because the Offner optical system is applied.

The fourth modification of the seventh embodiment is next describedreferring to FIG. 44, FIG. 44 is a plan view of the fourth modificationin which an Offner optical system and an optical member for correctingastigmatism generated in the Offner optical system are applied in thepresent invention. In FIG. 44, members with like functions as those inthe embodiment of FIG. 39 and the third modification of FIG. 44 aredenoted by the same reference numerals, and the same coordinate systemas in FIG. 43 is employed.

In FIG. 44, the polarizing beam splitter 7PR1 having the polarizationseparating surface 7R1 is provided in the optical path between theconcave mirror 704 in the Offner optical system and the mask 8, and thepolarizing beam splitter 7PR2 having the polarization separating surface7R2 is provided in the optical path between the concave mirror 704 andthe plate 9. A quarter wave plate 7H5 is disposed in the optical pathbetween the polarizing beam splitters 7PR1, 7PR2 and the concave mirror704. On the opposite side to the concave mirror 704 with respect to thepolarizing beam splitters 7PR1, 7PR2 there are two reflective mirrors7M1, 7M2 for transferring a light beam of from the polarizing beamsplitter 7PR2 in the direction perpendicular to the optical axis Ax toguide it to the polarizing beam splitter 7PR1. Also, an astigmatismcorrecting member 7MS of a meniscus shape with a convex surface to theconcave mirror 704 is disposed in the optical path between thesereflective mirrors 7M1, 7M2 and the polarizing beam splitters 7PR1,7PR2. Further, the present modification is so arranged that a field stopFS having an aperture portion of an arcuate shape is provided in theoptical path between the two reflective mirrors 7M1, 7M2.

Next, the optical path in the forth modification of the seventhembodiment is described referring to FIG. 44. In FIG. 44, theillumination optical system 701 uniformly illuminates a predeterminedillumination region on the mask 8 with linearly polarized light in thedirection normal to the plane of drawing (s-polarized light with respectto the polarization separating surfaces 7R1, 7R2 in the polarizing beamsplitters 7PR1, 7PR2), similarly as in the seventh embodiment.

In FIG. 44, the s-polarized light from the mask 8 illuminated by theillumination optical system 701 is reflected by the polarizationseparating surface 7R1 in the polarizing beam splitter 7PR1 andthereafter passes through the quarter wave plate 7H5 to be convertedinto circularly polarized light. Then the circularly polarized light isreflected by the concave mirror 704, convex mirror 705, and concavemirror 704 in this order then to pass through the quarter wave plate 7H5to be converted into p-polarized light. This p-polarized light passesthrough the polarizing beam splitter 7PR2 and then through theastigmatism correcting member 7MS and thereafter the optical paththereof is deflected 90° by the reflective mirror 7M1 to reach the fieldstop FS. Here, a primary image of mask 8 is formed in the apertureportion of field stop FS with the Z-directional lateral magnificationbeing +1 and the Y-directional lateral magnification being −1, similarlyas in the present embodiment. The optical path of the p-polarized lightfrom the primary image is deflected 90° by the reflective mirror 7M2 andthe p-polarized light passes through the astigmatism correcting member7MS and then through the polarizing beam splitter 7PR1. The p-polarizedlight passing through this polarizing beam splitter 7PR1 then passesthrough the quarter wave plate 7H5 to be converted into circularlypolarized light, and thereafter travels via the concave mirror 704,convex mirror 705, and concave mirror 704 in this order to pass throughthe quarter wave plate 7H5 to be converted into s-polarized light. Thiss-polarized light is reflected by the polarizing beam splitter 7PR2 andthereafter passes through the magnification correcting optical system Mto reach the plate 9. By this, a real-size erect image of mask 8 isformed on the plate 9 with the Y-directional and Z-directional lateralmagnifications both being +1.

Since the present modification is so arranged that the astigmatismcorrecting member 7MS can correct astigmatism generated in the Offneroptical system, the width (slit width) of exposure region in thescanning direction can be expanded, thereby improving the throughput.Further, because the present modification is so arranged that theastigmatism correcting member 7MS is set as coaxial with the opticalaxis Ax of the Offner optical system, it can enjoy such an advantagethat adjustment of the astigmatism correcting member 7MS is easy. Thisastigmatism correcting member 7MS may be constructed of two separateoptical members, one disposed in the optical path between the polarizingbeam splitter 7PR2 and the reflective mirror 7M1 and the other in theoptical path between the reflective mirror 7M2 and the polarizing beamsplitter 7PR1.

The above third and forth modifications of FIG. 43 and FIG. 44 employthe Offner optical system as the projection optical system, but theDyson optical system may be applied. Next described referring to FIG. 45is the fifth modification of the seventh embodiment employing the Dysonoptical system as the projection optical system. FIG. 45 is a plan viewof the fifth modification of the seventh embodiment in which the Dysonoptical system is applied in the present invention. In FIG. 45, memberswith like functions as those in the first embodiment of FIG. 39 aredenoted by the same reference numerals, and the same coordinate systemas in FIG. 39 is employed.

In FIG. 45, provided between the mask 8 and plate 9 are a plano-convexlens 706 and a concave mirror 707 having the optical axis Ax parallel toan in-plane direction (YZ direction) of the mask 8 and plate 9. Here, anaperture stop AS is provided near the concave mirror 707. On theopposite side to the concave mirror 707 with respect to the plano-convexlens 706 there is provided a polarization separating element 7PR withtwo polarization separating surfaces 7R1, 7R2 as the first and secondlight splitting means. These polarization separating surfaces 7R1, 7R2are arranged as perpendicular to each other. On the opposite side to theplano-convex lens 706 with respect to the polarization separatingelement 7PR there are two reflective mirrors 7M1, 7M2 with respectivereflective surfaces thereof perpendicular to each other as the beamtransferring means. A field stop FS having an aperture portion of apredetermined shape is provided in the optical path between the tworeflective mirrors 7M1, 7M2. A quarter wave plate 7H6 is provided as aphase changing member in the optical path between the plano-convex lens706 and the concave mirror 707.

Next, the optical oath in the fifth modification of the seventhembodiment is described referring to FIG. 45. The illumination opticalsystem 701 shown in FIG. 45 is arranged to uniformly illuminate apredetermined illumination region on the mask 8 with linearly polarizedlight in the direction normal to the plane of drawing (s-polarized lightwith respect to the polarization separating surfaces 7R1, 7R2 in thepolarizing beam splitters 7PR1, 7PR2), similarly as in the firstembodiment.

In FIG. 45, the s-polarized light from the mask 8 illuminated by theillumination optical system 701 is reflected by the polarizationseparating surface 7R1 in the polarization separating element 7PR and isthen subjected to the refracting effect in the plano-convex lens 706.Then the s-polarized light is converted into circularly polarized lightby the quarter wave plate 7H6. This circularly polarized light isreflected by the concave mirror 707 and thereafter passes through thequarter wave plate 7H6 to be converted into p-polarized light. Thisp-polarized light passes through the polarization separating surface 7R2in the polarization separating element PR and the optical path thereofis deflected 90° by the reflective mirror 7M1 to reach the field stopFS. Here, a primary image of mask 8 is formed in the aperture portion offield stop FS with the Z-directional lateral magnification being +1 andthe Y-directional lateral magnification being −1, similarly as in theseventh embodiment. The optical path of the p-polarized light from theprimary image is deflected 90° by the reflective mirror 7M2 and then ispasses through the polarization separating surface 7R1 in thepolarization separating element 7PR to enter the plano-convex lens 706.The p-polarized light entering the plano-convex lens 706 then passesthrough the quarter wave plate 7H6 to be converted into circularlypolarized light. Then the circularly polarized light is reflected by theconcave mirror 707 and again passes through the quarter wave plate 7H6to be converted into s-polarized light. This s-polarized light passesthrough the plano-convex lens 706 and is reflected by the polarizationseparating surface 7R2 in the polarization separating element 7PR. Afterthat, the s-polarized light passes through the magnification correctingoptical system M to reach the plate 9. Here, a real-size erect image ofmask 8 is formed on the plate 9 with the Y-directional and Z-directionallateral magnifications both being +1.

The Dyson optical system shown in FIG. 45 is composed of oneplano-convex lens 706 and the concave mirror 707, but a plurality oflens components having a positive combinational refractive power mayreplace the one plano-convex lens 706.

Since the Dyson optical system is generally difficult to secure asufficient working distance, the optical system may be constructed in atype different from the so-called Dyson type by combining the concavemirror with a lens group while keeping the working distance long enough.For example, in the first embodiment shown in FIG. 39, it is conceivableto replace the plane reflective mirror 703 with a concave mirror.

In the above-described each modification of the seventh embodiment andthe seventh embodiment the prism type polarization separating elementwas used as the first and second polarization separating means, butinstead thereof, it is also possible to employ such an arrangement thata dielectric multilayer film is vapor-deposited over a surface of aplane-parallel plate and this surface is used as the polarizationseparating surface.

In the seventh embodiment and the first to fifth modifications of theseventh embodiment, it is desired that a quarter wave plate be providedin the optical path between the magnification correcting optical system7M and the polarizing beam splitter 7PR2. By this, the exposure lightreaching the plate 9 becomes circularly polarized light.

The projection optical systems according to the seventh embodiment andthe first to fifth modifications thereof as described above have aneffect of considerable decrease of cost because they can be constructedby a very small number of lens components as compared with theprojection optical systems for obtaining an erect image by simplycombining two refractive optical systems on a same axis. Further, theprojection optical systems can be constructed of a smaller number ofconstituent elements of projection optical system, which can loweroccurrence of fabrication errors etc., thus presenting an excellenteffect of easy adjustment of projection optical system itself.

The sixth modification of the seventh embodiment is next describedreferring to FIG. 46. FIG. 46 is a drawing to diagrammatically show thesixth modification of the seventh embodiment provided with a pluralityof projection optical systems in a zigzag arrangement to transfer thepattern on the entire surface of mask 8 onto the plate 9 by one scanningexposure. FIG. 46 employs the same coordinate system as FIG. 39, andmembers with like functions as those in the seventh embodiment of FIG.39 are denoted by the same reference numerals.

In FIG. 46, five projection optical systems PLa-PLe are provided in thespace between the mask 8 and the plate 9. Since the structure of theprojection optical systems PLa-PLe shown in FIG. 47 is the same as inthe seventh embodiment of FIG. 39, the description thereof is omittedherein. These projection optical systems PLa-PLe form real-size erectimages of field regions IFa-IFe, respectively on the mask 8, on exposureregions EFa-EFe on the plate 9.

In FIG. 46, the projection optical systems PLa, PLc, PLe are arranged sothat the field regions thereof IFa, IFc, IFe are aligned along the Ydirection, while the projection optical systems PLb, PLd are arranged sothat the field regions IFb, IFd thereof are aligned along the Ydirection. On this occasion, the Z-directional position where the fieldregions IFa, IFc, IFe are located is different from the Z-directionalposition where the field regions IFb, IFd are located.

The shape of each field region IFa-IFe shown in FIG. 46 is trapezoid,and the field regions IFa-IFe are located so that oblique sides of thefield regions IFa-IFe overlap with each other. Namely, each field regionIFa-IFe is positioned so that a sum of lengths in the Z direction(scanning direction), of the field regions IFa-IFe becomes alwaysconstant in the Y direction (the direction perpendicular to the scanningdirection).

Here, if the magnification is adjusted in each exposure region EFa-EFeby the magnification correcting optical system M shown in FIG. 39,positional relations between the exposure regions EFa-EFe deviate fromeach other so as to make exposure amounts on the plate 9 nonuniform.Although not shown, the seventh embodiment employs a plane-parallelplate arranged as rotatable in the Y,Z directions in each projectionoptical system PLa-PLe, and positions in the Y,Z directions, of eachexposure region EFa-EFe are adjusted by rotation of the plane-parallelplate.

The shape of each field region IFa-IFe is not limited to trapezoid, butit may be rectangular, hexagonal, or arcuate as long as the sum oflengths in the Z direction, of the field regions IFa-IFe is alwaysconstant.

Although not shown in FIG. 46, the sixth modification of the seventhembodiment includes a plurality of illumination optical systems on theopposite side to the projection optical systems PLa-PLe with respect tothe mask B. These illumination optical systems have respectivepolarizers in the optical paths thereof to supply linearly polarizedlight to the mask 8. Also, a laser for supplying linearly polarizedlight can also be applied as a light source in each illumination opticalsystem.

Upon actual exposure, while illuminating each field region IFa-IFe inthe mask 8 by the illumination optical system not shown, the mask 8 andplate 9 are moved together along the Z direction, whereby images ofpattern of mask 8 in the field regions IFa-IFe are serially formed onthe plate 9. By this, the pattern of mask 8 is transferred onto theplate 9.

Although the sixth modification employed the five projection opticalsystems, it is needless to mention that the present invention is by nomeans limited to the five projection optical systems. Further, theprojection optical systems do not have to be limited to the projectionoptical system in the seventh embodiment of FIG. 39, but any projectionoptical system in the first to fifth modifications may also be applied.

Since the above-described exposure apparatus shown in FIG. 46 canrealize exposure on a large-scale substrate by a single exposureoperation, the throughput can be improved. Further, the exposure regioncan be expanded without increasing the size of projection optical systemitself, thus presenting an advantage of not degrading the opticalperformance.

It is also conceivable that the exposure apparatus shown in FIG. 46 isarranged to include only two projection optical systems (for example,only the projection optical systems PLa, PLb) and that the exposuremethod of repeating the scanning exposure operation and step operationis performed as in the seventh embodiment shown in FIG. 39. Thethroughput can be improved in that case because the number of stepoperations can be decreased as compared with the seventh embodiment.

Next described referring to FIG. 47 is the illumination optical systemsuitable for the embodiment of FIG. 46. In FIG. 47, the same coordinatesystem as in FIG. 46 is employed and members with like functions asthose in the sixth modification of the seventh embodiment of FIG. 46 aredenoted by the same reference numerals.

In FIG. 47, a super-high pressure mercury lamp 710 supplies illuminationlight of a predetermined wavelength (for example, the g-line (436 nm) orthe h-line (404 nm)). The illumination light from the super-highpressure mercury lam 710 is collected by an ellipsoidal mirror 7PM totravel via a path bending mirror 7M10 and to pass through a collectorlens system 711 then to enter a light guide 712 consisting of a bundleof optical fibers. The illumination light emerging from the light guide712 is incident into a fly's eye lens 713 to form a plurality ofsecondary light source images on the exit plane of the fly's eye lens713. The illumination light from the exit plane of the fly's eye lens713 is split into two linearly polarized light beams having mutuallyorthogonal polarization directions by the polarizing beam splitter 714.

Here, the s-polarized light reflected by the polarizing beam splitter714 travels along the Y direction in the drawing and then is reflectedby a path bending mirror 7M11 so as to advance along the Z direction inthe drawing. Linearly polarized light from the path bending mirror 7M11will have an oscillation plane in the X direction in the drawing. Thelinearly polarized light having the oscillation plane in the X directionpasses through a half wave plate 7H7 to be converted into linearlypolarized light having an oscillation plane along the Y direction in thedrawing. The linearly polarized light is then reflected by a pathbending mirror 7M12 to reach a condenser lens 715 c. This condenser lens715 c is located so that the front focal point thereof is positioned onthe exit plane of the fly's eye lens 713, and the field region IFc onthe mask 8 is thus illuminated in a superimposed manner by the linearlypolarized light having the oscillation plane along the Y direction.

On the other hand, the p-polarized light passing through the polarizingbeam splitter 714 advances along the Z direction in the drawing and isthen reflected by a path bending mirror 7M13 whereby the optical paththereof is deflected to the Y direction in the drawing. Then the lighttravels toward a path bending mirror 7M14. On this occasion, thelinearly polarized light between the polarizing beam splitter 714 andthe path bending mirror 7M13 will have the oscillation plane along the Ydirection in the drawing, and the linearly polarized light between thepath bending mirror 7M13 and the path bending mirror 7M14 will have theoscillation plane along the Z direction in the drawing. The linearlypolarized light reflected by the path bending mirror 7M14 will have theoscillation plane in the Y direction in the drawing to advance along theZ direction, and the optical path thereof is deflected 90° by pathbending mirror 7M15 to advance along the X direction. The linearlypolarized light from this path bending mirror 7M15 becomes linearlypolarized light having the oscillation plane in the Y direction in thedrawing, which passes through a condenser lens 715 a to reach the mask8. This condenser lens 715 a is also located so that the front focalpoint thereof is positioned on the exit plane of the fly's eye lens 713,similarly as the condenser lens 715 c, so that the field region IFa onthe mask 8 is illuminated in a superimposed manner by the linearlypolarized light having the oscillation plane along the Y direction.

By this, the field regions IFa, IFc become s-polarized with respect tothe polarization separating surfaces in the polarizing beam splittersPR1 a, PR1 c in the respective projection optical systems PLa, PLc.Since the illumination optical system for illuminating the field regionsIFb, IFd has the same structure as the illumination optical system forilluminating the field regions IFa, IFc, the description thereof isomitted herein.

As described, the illumination optical system as shown in FIG. 47 canconsiderably decrease losses in the light from the light source when aplurality of regions are illuminated with linearly polarized light in amutually equal polarization state. The illumination optical system caralso be constructed in the structure shown in FIG. 48. A modification ofthe illumination optical system is next described referring to FIG. 48.In FIG. 48, the same coordinate system as in FIG. 47 is employed andmembers with like functions as those in the illumination optical systemof FIG. 47 are denoted by the same reference numerals.

In FIG. 48, the illumination light from the super-high pressure mercurylamp 710 is collected by the ellipsoidal mirror 7PM and is incidentthrough the collector lens system 711 into the fly's eye lens 713 toform a plurality of secondary light source images on the exit plane ofthe fly's eye lens 713. The illumination light from the exit plane ofthe fly's eye lens 713 is split into two linearly polarized light beamshaving mutually orthogonal polarization directions by the polarizingbeam splitter 714.

Here, the s-polarized light reflected by the polarizing beam splitter714 becomes linearly polarized light having the oscillation plane in theZ direction in the drawing to advance along the Y direction in thedrawing and then to reach a path bending mirror 7M21. The linearlypolarized light reflected by the path bending mirror 7M21 advances alongthe X direction in the drawing and is reflected by a path bending mirror7M22 with the oscillation plane in the Y direction. The linearlypolarized light reflected by the path bending mirror 7M22 is deflectedso as to advance in the Z direction, becoming linearly polarized lightwith the oscillation plane in the X direction. The linearly polarizedlight then reaches a path bending mirror 7M23. The linearly polarizedlight reflected by the path bending mirror 7M23 and traveling in the Xdirection will have the oscillation plane in the Z direction, and thenpasses through a half wave plate 7H8 to have the oscillation planethereof in the Y direction. The linearly polarized light with theoscillation plane in the Y direction is condensed by the condenser lens715 a having the front focal point on the position of the exit plane ofthe fly's eye lens 713 to illuminate the field region IFa in the mask 8in a superimposed manner.

On the other hand, the p-polarized light transmitted by the polarizingbeam splitter 714 becomes linearly polarized light having theoscillation plane in the Y direction in the drawing and advances alongthe X direction in the drawing to reach a path bending mirror 7M24. Thelinearly polarized light reflected by the path bending mirror 7M24travels along the Z direction in the drawing and then is reflected by apath bending mirror 7M25 so as to travel toward a path bending mirror7M26 along the optical path extending in the X direction. The linearlypolarized light reaching the path bending mirror 7M26 is deflected bythe path bending mirror 7M26 so that the optical path thereof runs inthe Z direction, and reaches a path bending mirror 7M27. The linearlypolarized light reflected by this path bending mirror 7M27 travels alongthe X direction in the drawing and then is condensed by the condenserlens 715 having the front focal point located on the exit plane of thefly's eye lens 713 to illuminate the mask 8 in a superimposed manner.Here, because the oscillation plane of the linearly polarized light isnot rotated by the path bending mirrors 7M24-7M27 in the optical pathfrom the polarizing beam splitter 714 to the mask 8, the linearlypolarized light having the oscillation plane in the Y direction in thedrawing passes in this optical path. Accordingly, the field region IFcon the mask B is illuminated in a superimposed manner by the linearlypolarized light having the oscillation plane in the Y direction, comingfrom the condenser lens 715 c.

By this, the field regions IFa, IFc are illuminated in the s-polarizedstate with respect to the polarization separating surfaces in thepolarizing beam splitters PR1 a, PR1 c in the projection optical systemsPLa, PLc. The illumination optical system of FIG. 47 is so arranged thatthe optical path length from the polarizing beam splitter 714 to thefield region IFa becomes equal to the optical path length from thepolarizing beam splitter 714 to the field region IFc.

Since the illumination optical system for illuminating the field regionsIFb, IFd is constructed in the same structure as the illuminationoptical system for illuminating the field regions IFa, IFc, illustrationthereof is omitted in FIG. 48.

As described, the illumination optical system shown in FIG. 48 can alsoconsiderably decrease losses in the light from the light source when aplurality of regions are illuminated by the linearly polarized light ofa same polarization state. Further, because in the optical system shownin FIG. 48, X-directional positions are different between the pathbending mirrors 7M23, 7M27 for deflecting the light from the polarizingbeam splitter ?14 traveling along the Z direction, to the X direction,the path bending mirrors 7M23, 7M27 can be constructed in a large scalewithout interference therebetween. Namely, the freedom of arrangement ofthe path bending mirrors 7M23, 7M27 can be increased.

In the illumination optical systems shown in FIG. 47 and FIG. 48, a halfwave plate rotatable about the traveling direction of light may beinterposed in each of two optical paths separated by the polarizing beamsplitter 714. Here, rotating the half wave plate in each optical path,the oscillation plane of linearly polarized light reaching each fieldregion rotates, whereby an exposure amount in each exposure regioncorresponding to the each field region can be changed.

As described, the illumination optical systems shown in FIG. 47 and FIG.48 can supply the illumination light of linearly polarized light to aplurality of regions without losing the light from light source.

Here, in the above eight embodiment, an optical system is arranged tohave at least one reflective surface coaxial with the optical axisthereof, and the structure is thus half decreased as compared with mere,refractive optical systems, because an image of object is formed bylight passing back and forth through the optical system by means of thereflective surface. Further, because the projection optical systemaccording to the present invention is so arranged that a real-size erectimage of mask is formed on a substrate by two round passages of lightthrough the optical system, the structure can be quarter as comparedwith optical systems for obtaining an erect image by a simplecombination of two coaxial refractive optical systems. Accordingly, thepresent invention permits the number of constituents in the Projectionoptical system to be largely curtailed, thus presenting an advantagethat the effect of cost reduction is very high.

Further in the seventh embodiment, the erect image means an image withthe lateral magnifications in the vertical direction and the horizontaldirection both being positive. In the seventh embodiment as describedabove, for example as shown in FIG. 39, it is preferred that the opticalsystem be disposed on one side of first and second light splitting meansand that a beam transferring member for transferring a light beampassing the second light splitting means along the direction traversingthe optical axis be disposed on the other side of the first and secondlight splitting means.

In the seventh embodiment as described above, for example as shown inFIGS. 42A and 42B, it is preferred that the optical system be disposedon one side of the first and second light splitting means, that a firstdeflecting member for guiding light from the mask to the first lightsplitting means be disposed on the other side of the first lightsplitting means, and that a second deflecting member for guiding lightfrom the second light splitting means to the substrate be disposed onthe other side of the second light splitting means.

More further in the seventh embodiment, for example as shown in FIG. 39,it is desired that the first and second light splitting means bepolarizing beam splitters and that a phase changing member for changingthe phase between mutually orthogonal polarization components bedisposed in the optical path running from the first light splittingmeans through the optical system to the second light splitting means.This arrangement enables exposure to be made in a very low state oflosses in quantity of light in the first and second light splittingmeans. Further, because the direction of an oscillation plane oflinearly polarized light in which the light from the mask first passesback and forth through the optical system can be made different from thedirection of an oscillation plane of linearly polarized light in whichthe light next passes back and forth through the optical system, flareand double images can be prevented, thus improving the opticalperformance.

The exposure apparatus according to the seventh embodiment is preferablyarranged, for example as shown in FIG. 46, in such a manner that theapparatus is provided with an illumination optical system having a lightsource and a polarizing beam splitter for splitting light from the lightsource, guiding one light split into by the polarizing beam splitter toa first field region, and guiding the other light split into by thepolarizing beam splitter to a second field region. This arrangementrealizes the structure for guiding the light from a light source to aplurality of field regions without losses in quantity of light.

Further, it is desired that a phase changing member for changing thephase between mutually orthogonal polarization components be disposed inthe optical path between the polarizing beam splitter and the first orsecond field region. Since this arrangement permits the phase changingmembers to make polarization states of light beams guided to a pluralityof field regions in a same polarization state, light splitting means ina plurality of projection optical systems can be constructed in the samestructure. This can reduce the production cost.

It is also preferred in the seventh embodiment that a field stop beprovided in the optical path running from the first light splittingmember (7PR1) to the second light splitting member. This arrangement candecrease flare due to the optical system (702, 703).

In the seventh embodiment, the optical system may be arranged, forexample as shown in FIG. 39, to have a lens unit, and a plane reflectivemirror disposed near the position of the focal point of the lens unit.This arrangement is very simple as including a quarter number of lenscomponents as compared with the arrangement using simply two refractiveoptical systems for obtaining an erect image.

In the modification of the seventh embodiment, the optical system may bearranged, for example as shown in FIGS. 42A and 42B, to have a convexmirror (705) and a concave mirror (704) coaxially arranged, or may bearranged, for example as shown in FIG. 44, to have a concave mirror(707) and a lens component (706) coaxially arranged.

It is preferred that the optical system (702, 703) in the modificationof the seventh epresent invention be a both side telecentric opticalsystem.

In the seventh embodiment, it is desired, for example as shown in FIG.39, that the optical axis (Ax) of the optical system (702, 703) beparallel to an in-plane direction (YZ direction) of the mask (8) orsubstrate (9). This arrangement can decrease the size of the opticalsystem (702, 703) in the direction normal to the mask (substrate). Thus,the distance can be decreased between the mask (8) and the substrate(9), thus enhancing the stiffness of a carriage for supporting thesemask (8) and substrate (9).

In the seventh embodiment it is preferred, for example as shown in FIG.39, that the first light splitting member (7PR1) reflect the light fromthe mask (8) to the optical system (702, 703) and that the second lightsplitting member (7PR2) transmit the light coming from the first lightsplitting member (7PR1) through the optical system (702, 703) to guideit to the beam transferring member (7M1, 7M2) but reflect the lightcoming from the beam transferring member (7M1, 7M2) through the firstlight splitting member (7PR1) and the optical system (702, 703) to guideit onto the substrate (9).

Further, it is preferred in the seventh embodiment that an opticalelement for converting linearly polarized light traveling from thesecond light splitting member to the substrate into circularly polarizedlight be disposed in the optical path between the second light splittingmember and the substrate.

Next the eighth embodiment of the projection optical system will beexplained below, referring to FIGS. 49-54D. The projection opticalsystem corresponds to those of the previous embodiments and the otherelements except for the projection optical system is the same as thoseof the previous embodiments.

FIG. 49 is a drawing to show the structure of the eighth embodimentaccording to the present invention. In FIG. 49, the Z axis is takenalong the scanning direction of the mask as a first object and the plateas a second object, the Y axis along the direction perpendicular to thescanning direction in the mask plane, and the X axis along the directionnormal to the mask and the plate.

In FIG. 49, the illumination optical system IL has, for example, asuper-high pressure mercury lamp, which illuminates the mask 8 at thewavelength of exposure light (for example, the g-line (435.8 nm)). Here,the mask 8 has a circuit pattern not shown, and is held by a mask stageMS so that this circuit pattern faces the plate 9 (down in the drawing).This mask stage MS is arranged as movable within the YZ plane in thedrawing. The plate 9 is, for example, a glass substrate coated with aphotoresist on the surface thereof, and is held by a plate stage PSarranged as movable within the YZ plane in the drawing.

These mask stage MS and plate stage PS are mounted in a united manner ona carriage C having a C-shaped cross section on the XY plane, as shownin FIG. 50. This carriage C is arranged as movable within the YZ plane.

Returning to FIG. 49, an image-forming lens for projection 20 having theoptical axis along the Z direction is disposed between the mask 8 andthe plate 9. On one side of the projection image-forming lens 820 thereis provided a reflective member 10 having a reflective surface 10 ainclined at 45° relative to the mask 8 and a reflective surface 810 binclined at 45° relative to the plate 9. On the other side of theprojection image-forming lens 820 there are provided, as a beamtransferring member, a reflective member 813 having a reflective surface13 a inclined at 45° relative to the optical axis of the projectionimage-forming lens 820 and a reflective member 815 having a reflectivesurface 815 a inclined at 45° relative to the optical axis of theprojection image-forming lens 820. Here, the reflective surface 813 aand reflective surface 815 a are arranged as perpendicular to eachother.

The projection image-forming lens 820 has a front group GF of a positiverefractive power as a whole including lens components L1-L4, an aperturestop AS for defining the numerical aperture of the projectionimage-forming lens 820, and a rear group GR of a positive refractivepower as a whole including lens components L5-L8. In the eighthembodiment, the front group GF and rear group GR have the same structureand are so arranged that the position of the rear focal point of thefront group GF and the position of the front focal point of the reargroup GR are located at the position of the aperture stop AS.Accordingly, the projection image-forming lens 820 is a both sidetelecentric optical system.

Also, the reflective member 810 is mounted on a support member 811 fixedto the main body of exposure apparatus, and the reflective members 813,815 are mounted on a support member 816 similarly fixed to the main bodyof exposure apparatus. The lens components L1-L8 and aperture stop inthe projection image-forming lens 820 are mounted in a lens barrel 812fixed to the main body of exposure apparatus. Now, light from the mask 8illuminated by the illumination optical system IL is deflected 90° inoptical path by the reflective surface 810 a to advance along thedirection of the optical axis (Z direction) of the projectionimage-forming lens 820 and then to reach the lens component L1 in theprojection image-forming lens 820. This light successively passesthrough the lens components L1-L4 then to reach the aperture stop AS.The light passing through the aperture stop AS successively passes thelens components L5-L8 and thereafter is emergent therefrom in parallelwith the optical axis of the projection image-forming lens 820. Thelight emergent from the projection image-forming lens 820 is deflected90° in optical path by the reflective surface 813 a to advance to thefield stop 814 fixed to the support member 816. Since the field stop 814is located at a position conjugate with the mask 8 with respect to theprojection image-forming lens 820, an intermediate image of the mask 8is formed here. This intermediate image has the lateral magnification inthe Y direction of −1 and the lateral magnification in the Z directionof +1.

Next, the light from the intermediate image on the field stop 814 isdeflected 90° in optical path by the reflective surface 15 a so as toadvance in parallel with the optical axis of the projectionimage-forming lens 820 and then to reach the lens component L8 in theprojection image-forming lens 820. This light successively passes thelens components L8-L5, the aperture stop AS, and the lens componentsL4-L1, and thereafter is emergent in parallel with the optical axis ofthe projection image-forming lens 820. The light from the projectionimage-forming lens 820 is deflected 90° in optical path by thereflective surface 810 b to reach the plate 9. Here, since the fieldstop 814 and plate 9 are arranged as conjugate with each other withrespect to the projection image-forming lens 820, a secondary image ofmask 8 is formed on the plate 9. This secondary image of mask 8 is areal-size erect image with the Y-directional and Z-directional lateralmagnifications both being +1. In this manner, the eighth embodimentobtains the erect image by four reflections on the reflective surfacesand two image formations by the projection image-forming lens.

The eighth embodiment uses the same structure for the front group GF andthe rear group GR. Namely, since the focal length of the front group GFis equal to the focal length of the rear group GR, the mask 8 and theintermediate image on the field stop 814 are in a relation ofmagnification of 1, and the intermediate image on the field stop 14 andthe secondary image on the plate 9 are in a relation of magnification of1.

In the eighth embodiment, however, the magnification relation betweenthe mask 8 and the secondary image on the plate 9 is 1 even if the focallengths of the front group GF and the rear group GR are different fromeach other. Namely, when the magnification relation between the mask 8and the intermediate image on the field stop 814 is β(≠±1), themagnification relation between the intermediate image and the secondaryimage on the plate 9 becomes 1/β. It is thus understood that themagnification relation between the mask 8 and the secondary image on theplate is 1 as a whole. For example, if the magnification between themask 8 and the intermediate image on the field stop 814 is increased,separations between the reflective surfaces 810 a or 810 b in thereflective member 10 and the mask 8 or plate 9 (i.e. working distances)can be expanded. Therefore, the projection optical system according tothe eighth embodiment has an advantage of high freedom for opticdesigning.

The exposure operation in the eighth embodiment is briefly described inthe following with reference to FIG. 50. The following description showsan example of exposure in which the area on the mask 8 is divided intothree regions m1-m3 and the regions m1-m3 are projected for exposure inthree regions p1-p3 on the plate 9.

Upon second or further exposure on the plate 9, a positional deviationbetween the mask 8 and the plate 9 is first detected using an alignmentoptical system not shown and based on the detection result, alignment ismade by moving at least one of the mask stage MS and the plate stage PSin the YZ plane.

After that, driving the carriage C, positioning is made so that theZ-directional edge of the region m1 in mask 8 and the Z-directional edgeof the region p1 in plate 9 are located in the field of the projectionimage-forming lens 820. Then the carriage C is moved at a predeterminedspeed along the Z direction (scanning direction) while the illuminationoptical system IL omitted in FIG. 50 illuminates the mask 8. By this, animage of the region m1 in the mask 8 is serially formed in the region p1on the plate 9.

Next, the carriage C is moved along the Y direction (the directionperpendicular to the scanning direction) in the drawing so as toposition the region m2 on the mask 8 and the region p2 on the plate 9 ascoincident with each other. After that, the carriage C is moved at thepredetermined speed along the Z direction (scanning direction) toserially form an image of the region m2 in the mask 8 on the region p2on the plate 9.

Finally, the carriage C is moved along the Y direction (the directionperpendicular to the scanning direction) in the drawing so as toposition the region m3 on the mask 8 and the region p3 on the plate 9 ascoincident with each other. After that, the carriage C is moved at thepredetermined speed along the Z direction (scanning direction) toserially form an image of the region m3 in the mask 8 on the region p3on the plate 9.

Here, in the above exposure operation, the moving direction of carriageC upon scanning exposure of the regions m1, m3 in the mask 8 isdifferent 180° from the moving direction of carriage C upon scanningexposure of the region m2 in the mask 8.

The positioning operation using the alignment optical system not shownmay be omitted upon first exposure on the plate 9.

In the eighth embodiment the carriage C is arranged as movable in the YZplane; if the carriage C is arranged as movable only in the Z direction,the mask stage MS and plate stage PS may be arranged to move in the Ydirection, which is equivalent to moving the carriage C in the Ydirection.

In the eighth embodiment, if the projection image-forming lens 820 is aone-side telecentric optical system, in order to achieve telecentricityat least on the plate 9 side, the reflective member 810 as a fieldsplitting member should be set on the telecentric side while thereflective members 813, 815 on the non-telecentric side. This achievestelecentricity on the mask 8 side and the plate 9 side. On thisoccasion, the reflective surfaces 813 a, 815 a of the respectivereflective members 813, 815 should be arranged in such a manner thatwith respect to the optical axis of the projection image-forming lens820 principal rays of light beams traveling from the projectionimage-forming lens 820 to the reflective surface 813 a are symmetricwith principal rays of light beams traveling from the reflective surface815 a to the projection image-forming lens 820. Since such a one-sidetelecentric optical system as described above includes a possibilitythat the magnification of the secondary image of mask 8 on the plate 9is partially different in the Z direction, the projection image-forminglens 820 is preferably constructed of a both side telecentric opticalsystem.

The eighth embodiment shown in FIG. 49 and FIG. 50 effects exposure bythe operation of moving the mask 8 and plate 9 in the directionperpendicular to the scanning direction, but exposure may be effected bysingle scan with a plurality of projection optical systems.

The exposure apparatus provided with a plurality of projection opticalsystems according to the eighth embodiment is next described referringto FIG. 51. FIG. 51 is a diagrammatic drawing to show an arrangement ofthe plurality of projection optical systems. In FIG. 51, members withlike functions as those in FIG. 49 and FIG. 50 are denoted by the samereference numerals, and the same coordinate system as in FIG. 49 andFIG. 50 is employed.

In FIG. 51, five projection optical systems 821-825 are disposed in thespace between the mask 8 and the plate 9. In the eighth embodiment, theentire optical system having the projection image-forming lens 820 inFIG. 49, the reflective member 810, the reflective members 813, 815, andthe field stop 814 is called as a projection optical system. Eachprojection optical system 821-825 forms a real-size erect image of afield region ML1-ML5 on the mask 8 in an exposure region PL1-PL5 on theplate 9.

The projection optical systems 821-823 are arranged so that the fieldregions ML1-ML3 are aligned along the Y direction, while the projectionoptical systems 824, 825 are arranged so that the field regions ML4, ML5are aligned along the Y direction. Here, the Z-directional positionwhere the field regions ML1-ML3 are located is different from theZ-directional position where the field regions ML4, ML5 are located.FIG. 51 shows an example in which shapes of each field region ML1-ML5and each exposure region PL1-PL5 are slit (rectangular), but the shapesare arbitrary as long as a sum of lengths in the Z direction (scanningdirection), of the field regions ML1-ML5 is always constant in the Ydirection (the direction perpendicular to the scanning direction).Specifically, conceivable shapes are hexagonal, arcuate, or trapezoid.The shapes will be detailed hereinafter.

Upon actual exposure, the illumination optical system not shownilluminates the mask 8, and the mask 8 and plate 9 are moved togetheralong the Z direction, whereby the field regions ML1-ML5 scan the entiresurface on the mask 8 and the exposure regions PL1-PL5 scan the entiresurface on the plate 9. By this, an image of mask 8 is seriallysuccessively formed on the plate 9.

Since in the exposure apparatus having the projection optical systems821-823 and the projection optical systems 824, 825 are so arranged thatthe reflective members 813, 815 thereof as beam transferring members areopposed to each other, separations in the direction perpendicular to thescanning direction (or in the Y direction) can be decreased between theexposure regions PL1-PL3 and the exposure regions PL4, PL5, which isconvenient in respect of layout.

It is noted that the number of projection optical systems is not limitedto 5 in the second embodiment.

The projection image-forming lens 820 according to the exposureapparatus shown in FIG. 51 preferably satisfies the following condition.

Φ/2<d  (1)

where Φ: the maximum lens diameter of the projection image-forming lens820;

d: the working distance of the projection image-forming lens 820.

The above working distance d is a distance obtained by ignoring bendingof optical path by the reflective surface 810 a of reflective member810, as shown in FIG. 52B which is an enlarged drawing of the projectionoptical system on the mask 8 and plate 9 side.

Unless the projection image-forming lens 820 satisfies the abovecondition of Equation (1), the mask 8 interferes with the projectionimage-forming lens 820 (or lens barrel 12), which is not preferred.

Since in the exposure apparatus shown in FIG. 51 the field of theprojection image-forming lens 20 is divided into two by the reflectivemember 810, an eclipse appears in the field region near the optical axisof the projection image-forming lens 820, as shown in FIG. 53A. In FIG.53A the dashed line represents the entire field of the projectionimage-forming lens 820 as observed along the Z direction, and the regionof effective field (non-eclipsed field) of the projection image-forminglens is indicated by hatching. In FIG. 52B and FIG. 53A, the length inthe Z direction, of the eclipse region on the mask 8 surface or theplate 9 surface, that is, the length X1min in the X direction, of theprojection image-forming lens 820 as observed along the Z direction, isexpressed by the following condition of Equation (2) where dL is adistance between the apex of the reflective member 810 and the objectpoint of the projection image-forming lens 820, and θ1 is an angleobtained from NA1=sin θ1 where NA1 is a numerical aperture of theprojection image-forming lens 20.

X 1min=dL·tan θ1  (2)

Here, the position of the object point of the projection image-forminglens 820 shown in FIG. 52B and the field of the projection image-forminglens 820 shown in FIG. 53A are those obtained by ignoring bending ofoptical path by the reflective surface 10 a of reflective member 10 asrepresented by the dashed lines in the drawing.

Since on the intermediate image side of the projection image-forminglens 20 the reflective members 813, 815 transfer the light beam in thedirection traversing the optical axis of the projection image-forminglens 20, an eclipse appears in the field region on the intermediateimage side of the projection image-forming lens 820, as shown in FIG.53B. In FIG. 53B the entire field region on the intermediate image sideof the projection image-forming lens 820 is represented by the dashedline and the effective field (non-eclipsed region) on the intermediateimage side of the projection image-forming lens 820 is indicated byhatching. In FIG. 52B and FIG. 53B, the length X2min in the X direction,of the eclipse region on the intermediate image plane is expressed bythe following condition of Equation (3) where dM is a distance betweenthe projection image-forming lens 820 and the intermediate image plane,and θ2 is an angle obtained from NA2=sin θ2 where NA2 is the numericalaperture of the projection image-forming lens 820.

X 2min=dM·tan θ2  (3)

Here, the distance between the projection image-forming lens 820 and theintermediate image plane shown in FIG. 52B and the field of theprojection image-forming lens 820 shown in FIG. 53B are those obtainedby ignoring bending of optical path by the reflective members 813, 815.

From the above, the field region and exposure region that can be used inthe projection optical system according to the exposure apparatus shownin FIG. 51 are an overlapping region between the two effective fieldsshown in FIG. 53A and FIG. 53B.

It is thus desired that an area of the aperture portion in the fieldstop 814 be within the above overlapping region between the effectivefields. FIGS. 54A-54D show relations between the shape of the apertureportion in the field stop 814 and the effective field of the projectionimage-forming lens 820. In FIGS. 54A-54D, the dashed lines represent theeffective field of the projection image-forming lens 820 on the plate 9and the solid lines images of aperture portions in the field stop 14projected by the projection image-forming lens 820. Here, the effectivefield of the projection image-forming lens 820 is the overlapping regionbetween the two effective fields shown in FIG. 53A and FIG. 53B.

FIG. 54A shows an example in which the field stop 814 has a slitaperture portion. For example, this type of slit aperture portion ispreferably used for cases of single scanning exposure with a projectionoptical system.

FIG. 54B shows an example in which the field stop 814 has a hexagonalaperture portion, FIG. 54C an example in which the field stop 814 has anarcuate aperture portion, and FIG. 54D an example in which the fieldstop 814 has a trapezoid aperture portion. As shown, the apertureportions in FIG. 54B to FIG. 54D each have portions where the length ofaperture opening portion in the Z direction (scanning direction) is notconstant. For example, in the case where two or more scanning exposuresare conducted by one projection optical system as shown in FIG. 50 or inthe case where a single scanning exposure is conducted by the pluralityof projection optical systems as shown in FIG. 51, the portions withlengths of aperture portion not constant should be set in the overlapregions. The overlap regions are regions where a plurality of exposureregions overlap with each other. On this occasion, a sum of lengths inthe Z direction, of the plurality of aperture portions in the overlapregions is always constant in the Y direction (the directionperpendicular to the scanning direction). By this arrangement,differences in exposure amount between the plurality of exposure regionsbecome always 0.

Here, as shown in FIG. 54A to FIG. 54D, the aperture portion in thefield stop 814 is arranged to be located within the effective field ofthe projection image-forming lens 820.

Next described referring to FIG. 55 is the ninth embodiment of theprojection optical system in which an optical member for correctingerrors due to environmental changes is incorporated. FIG. 55 is adrawing to show the structure of the projection optical system in theninth embodiment, which employs the same coordinate system as in FIG.49. In FIG. 55, members with like functions as those in the embodimentof FIG. 49 are denoted by the same reference numerals.

In FIG. 55, an arrangement different from that of the projection opticalsystem of FIG. 49 is that the projection optical system has a pressureadjusting portion 830 for changing the pressure of a gas confined in aspecific space between the plurality of lens components L1-L8 composingthe projection image-forming lens 820, and that a pair of plane-parallelplates 833, 34 disposed in the optical path between the reflectivesurface 810 a of the reflective member 810 and the plate 9.

The pressure adjusting portion 830 shown in FIG. 55 changes, through apipe 832, the pressure in a lens chamber 831, being a space hermeticallyclosed between the lens component L1 and the lens component L2, tochange the refractive index of the lens chamber 31, thereby changing theprojection magnification or the focal point position of the projectionimage-forming lens 820. A specific structure of the pressure adjustingportion 830 is disclosed in Japanese Patent Application No. 58-186267filed by the present applicant, and therefore, the description thereofis omitted herein.

The embodiment shown in FIG. 55 further has a control portion 835 forcontrolling the pressure adjusting portion 30, and an input portion 836,for example consisting of a keyboard etc., for inputting informationconcerning a desired projection magnification. The control portion 835includes a reference table storing relations between pressures in thelens chamber 831 and projection magnifications (lateral magnificationsof secondary image to the mask 8), and the control portion 835 controlsthe pressure adjusting portion 30 so that the pressure in the lenschamber 831 presents the desired projection magnification by referenceto the information concerning the magnification from the input portion836 and the reference table.

Next described are relations between a change amount of the focal lengthdue to pressure change and, magnification change amount and image planeposition change amount when the focal length of the front group GFchanges from f to f+Δ because of a pressure change in the lens chamber31. Actually, there exists a lens chamber strongly influencing thechange of projection magnification or a lens chamber largely changingthe image plane position, depending upon the refractive power of eachlens component in the projection image-forming lens 820. However, inorder to simplify the description, it is assumed that the focal lengthsof the front group GF and the rear group GR in the projectionimage-forming lens 20 both are f and that these front group GF and reargroup GR are approximate to thin lenses.

When the focal length of the front group GF changes from f to f+Δ asdescribed above, the magnification change and image plane positionchange at the intermediate image position are expressed as follows,applying the lens formulas for the front group GF and the rear group GR.

First, the image plane position change of the intermediate image isexpressed by the following equation:

f{(f+3Δ)/(f+2Δ)−1}  (4);

and the magnification change of the intermediate image is given by thefollowing equation:

−(f+Δ)/(f+2Δ)  (5).

Also, the image plane position change of the secondary image is given bythe following equation:

f{(f+3Δ)(f+Δ)}/(f(f+3Δ)−Δ(f+Δ)}  (6);

and the magnification of the secondary image at the secondary imageplane position, that is, the projection magnification is given by thefollowing equation:

(f+Δ)²/(f(f+3Δ)−Δ(f+Δ)}  (7).

Accordingly, if a change amount of the focal length of the front groupGF due to a change in pressure in the lens chamber 31 can be calculated,the magnification of the secondary image at the secondary image planeposition can be obtained and further, a change amount of the image planeposition of the secondary image can also be obtained. With a change ofthe image plane position of the secondary image the secondary image onthe plate 9 becomes defocused; in that case, either the mask 8 or theplate 9, or the both are moved along the X direction. The projectionoptical system of FIG. 55 includes one lens chamber for changing thepressure, but the lens chamber for changing the pressure is not limitedto one. For example, with two lens chambers, only the projectionmagnification can be changed while keeping the image plane positionchange of the secondary image expressed by the above Equation (7) at 0.The projection optical system of FIG. 55 includes the lens chamber forchanging the pressure only for the front group GF, but a lens chamberfor changing the pressure may be set in the rear group GR.

In the projection optical system shown in FIG. 55, a pair ofplane-parallel plates 833, 834 are provided in the optical path betweenthe reflective surface 10 b of the reflective member 10 and the plate 9.

In FIG. 55, the plane-parallel plate 833 is arranged as rockable about arotational axis along the Y direction, while the plane-parallel plate 34as rockable about a rotational axis along the Z direction. Here, whenthe plane-parallel plate 833 is rocked as inclined relative to the plate9, the position of the secondary image relative to the field of theprojection optical system can be moved in the Z direction. When theplane-parallel plate 834 is rocked as inclined relative to the plate 9,the position of the secondary image relative to the field of projectionoptical system can be moved in the Y direction.

Instead of the rocking of the plane-parallel plates, the position of thesecondary image can be moved by setting a pair of angular deflectionprisms having a wedge-shape cross section in the optical path betweenthe reflective surface 810 b and the plate 9 and changing a distancebetween these angular deflection prisms. Here, the pair of angulardeflection prisms are arranged to have planes making a specific apicalangle and to have respective apexes directed opposite to each other.

The operation for moving the position of the secondary image asdescribed above is not essential for cases of single scanning exposurewith a projection optical system or cases of plural scanning exposureswith a projection optical system as in the embodiment shown in FIG. 49and FIG. 50. It is, however, preferred that the pair of plane-parallelplates 33, 34 be provided for cases of single scanning exposure with aplurality of projection optical systems as shown in FIG. 51.

The embodiment shown in FIG. 51 is suitable, for example, forfabrication of large-screen liquid crystal panels; in fabricating suchlarge-screen liquid crystal panels, the plate 9 sometimes expands orcontracts by a process. Thus, the size of plate 9 upon first exposurewould be different from the size of plate 9 upon second exposure, forexample.

In that event, the pressure adjusting portion 30 may be used to changethe projection magnification upon second exposure from the projectionmagnification (magnification of the secondary image on the plate 9 tothe mask 8) upon first exposure. However, the plurality of exposureregions do not overlap with each other on the plate 9 if the projectionmagnification is changed.

This point is described in detail referring to FIG. 56. FIG. 56 is aplan view to show a relation between the field regions on the mask 8 andthe exposure regions on the plate 9 where the projection magnificationof the projection optical systems 21, 22 is of reduction. FIG. 56 showsan example in which the field regions and exposure regions are trapezoidand adjacent field regions and exposure regions are trapezoid asoriented as similar to each other.

In FIG. 56, the field regions ML1, ML2 on the mask 8 form secondaryimages thereof on the exposure regions PL1, PL2 on the plate 9 throughthe projection optical systems 821, 822 not shown. Since themagnification of exposure regions PL1, PL2 is of reduction, portions ofoverlap regions on the mask 8 do not overlap with each other on the mask8.

Thus, the plane-parallel plate 34 is rocked in the projection opticalsystem shown in FIG. 55 so as to move the exposure region PL2 in the Ydirection. On this occasion, a rocking angle of the plane-parallel plate834 is so determined as to make the overlap regions between the exposureregions PL1, PL2 come to overlap with each other in the Y direction onthe plate 9. The rocking angle of the plane-parallel plate can beobtained from the projection magnification of the projection opticalsystems 821-825, the size of the field regions ML1-ML5 of the projectionoptical systems 821-825, and the positions of the field regions ML1-ML5relative to the entire field of the projection optical systems.

The above-described example is arranged to move only the exposure regionPL2, but alternatively, the exposure region PL1 may be moved or both theexposure regions PL1, PL2 may be moved. Further, when the position ofexposure region PL1, PL2 needs to be moved in the Z direction, theplane-parallel plate 33 should be rocked in the projection opticalsystem shown in FIG. 55. The projection optical system shown in FIG. 55is arranged to adjust the pressure in the lens chamber in the projectionimage-forming lens 820 so as to change the projection magnification, butthe projection magnification may be changed by providing a lens of asmall refractive power near the field stop 814 and moving the lens alongthe optical axis. Such an example is described referring to FIG. 57.FIG. 57 employs the same coordinate system as FIG. 49. To simplify thedescription, members with like functions as those in the projectionoptical systems in FIG. 49 and FIG. 55 are denoted by the same referencenumerals.

In FIG. 57, lenses 841, 842 are disposed on either side of the fieldstop 814 in the optical path between the reflective surface 13 a and thereflective surface 15 a. These lenses 841, 842 are movable along theoptical-axis direction. Here, moving the lenses 841, 842 along theoptical-axis direction, a total focal length of the projectionimage-forming lens 820 and the lens 841 or a total focal length of theprojection image-forming lens 820 and the lens 842, or the both change.This can change the projection magnification of the overall projectionoptical system.

Here, for changing the magnification of the field stop 814 (themagnification of an image of the field stop 814 projected on the plate9), the above lenses 841, 842 should be disposed in the optical path onthe side of the reflective surface 815 a with respect to the field stop814. For cases not to change the magnification of field stop 814, theabove lenses 841, 842 should be disposed in the optical path on the sideof the reflective surface 13 a with respect to the field stop 814.

In the case where the projection optical systems shown in FIG. 55 orFIG. 57 are applied to the exposure apparatus shown in FIG. 51, it ispreferred that inputting means for inputting information concerning anamount of expansion or contraction of plate 9 be provided and that,based on the information concerning an amount of expansion orcontraction, magnification control be made for the plurality ofprojection optical systems 821-825. In that case it is preferred that arelation between amounts of expansion or contraction and pressures inthe lens chamber (in case of FIG. 55) or moving amounts of lenses 841,842 (in case of FIG. 57) be stored in the form of reference table. Here,if the magnification of projection optical system is changed in order tocorrect expansion or contraction of plate 9, movement of the secondaryimage by each projection optical system 821-825 needs to be corrected;it is thus preferred that the above reference table store a relationbetween expansion or contraction amounts and rocking angles of theplane-parallel plates 833, 834.

If the plate 9 is partially expanded or contracted, the magnificationsof projection optical systems 821-825 and moving amounts of therespective secondary images may be controlled independently of eachother.

Further, when the projection optical system of FIG. 55 is applied to theexposure apparatus shown in FIG. 51, the projection optical systems821-825 may be controlled by a single pressure adjusting portion. Inthat case, lens chambers formed in the respective projection opticalsystems 821-825 are arranged to be one space, and the pressure adjustingportion controls the pressure in this space.

In the projection optical systems shown in FIG. 49, FIG. 55 and FIG. 57,the reflective surfaces 813 a, 815 a as the beam transferring member maybe constructed of dichroic mirrors for reflecting the exposure light buttransmitting light of wavelengths different from that of the exposurelight (for example, wavelengths longer than the exposure light). Whenthe reflective surfaces 813 a, 815 a are constructed of dichroicmirrors, an alignment optical system may be disposed on the transmissionside of either the reflective surface 813 a or the reflective surface815 a or each of the reflective surfaces 813 a, 815 a. This arrangementpermits position detection between the mask 8 and the plate 9 throughthe projection optical system; so-called alignment of the TTL (Throughthe Lens) method.

Next described is the adjusting method of projection optical systemaccording to the present embodiment. First, aberration, magnification,and telecentricity of the projection image-forming lens 820 arecontrolled to specific values. After the angle is adjusted to 90°between the reflective surface 810 a and the reflective surface 810 b inthe reflective member 810, it is fixed to the supporting member 811.After the angle is adjusted to 90° between the reflective surface 813 aof reflective member 813 and the reflective surface 815 a of reflectivemember 815, it is fixed to the supporting member 816. After that, thelens barrel 812 of the projection image-forming lens 820 is fixed to themain body of exposure apparatus. Next, the supporting member 816 ispositioned so that the reflective surfaces 813 a, 815 a each make 45°relative to the optical axis of the projection image-forming lens 820,and this supporting member is fixed to the main body of exposureapparatus. Finally, the supporting member 811 is positioned so that thereflective surfaces 810 a, 810 b each make 45° relative to the opticalaxis of the projection image-forming lens, and this supporting member811 is fixed to the main body of exposure apparatus.

By the above described adjusting method, errors due to the reflectivesurfaces 810 a, 810 b, 813 a, 815 a can be obtained separately fromerrors due to the projection image-forming lens 820; thus, it is easilyrecognized what part needs to be controlled, thereby presenting anadvantage of easy adjustment of the entire projection optical system.

In the projection optical system in the above-described each embodiment,the reflective member 810 as the field splitting member is arranged tohave the reflective surfaces 810 a, 810 b; but this reflective member 10may be constructed of a prism. Further, the reflective surfaces 810 a,810 b are integrally formed on the reflective member 810, but they maybe divided into a member having the reflective surface 810 a and amember having the reflective surface 810 b. Further, if each reflectivemember 810, 813, 815 is arranged as rotatable about the X, Y, Z axes,there is an advantage that adjustment of the entire projection opticalsystem becomes possible.

Further, since the exposure apparatus in the above-described eighth,tent and tenth embodiments can also obtain the erect image of mask 8 bya projection optical system, the distance between the mask 8 and theplate 9 can be shortened. This presents an advantage of easiness toenhance the stiffness of carriage C for moving the mask 8 and plate 9together.

The above adjusting method as described above can facilitate opticaladjustment such as adjustment of deviation of optical axis or adjustmentof aberration. Generally, in the case where a reflective surface ispresent at the position of the pupil of projection optical system, therearises a problem that the image position of projection optical systemmoves depending upon inclination of the reflective surface; but, in theeighth and ninth embodiments, there exists no member for deflectinglight at the pupil position of projection optical system, therebyenabling to stabilize the image position.

Next an another embodiment of the exposure apparatus according to thepresent invention will be explained below.

FIG. 58 is a drawing to schematically show an embodiment of the exposureapparatus according to the present invention. In FIG. 58, the Zdirection is taken along the scanning direction of the mask 8 and theplate 9, the Y direction along the direction perpendicular to thescanning direction in the plane of mask 8 or plate 9, and the Xdirection along the direction normal to the mask 8 and plate 9.

In FIG. 58, five illumination optical systems ILa-ILe each form fiveillumination regions MIa-MIe on the mask 8. Since these illuminationoptical systems ILa-ILe each have the same structure, only the structureof illumination optical system ILa is described herein.

The light source la is, for example, a super-high pressure mercury lampemitting exposure light of the g-line (435.8 nm) or the h-line (404.7nm). The exposure light from the light source la is reflected andcollected by an ellipsoidal mirror 92 a and then passes through an inputlens not shown to become a parallel light beam, which is incident intoan optical integrator 93 a. The optical integrator 93 a is constructed,for example, of a fly's eye lens, which forms a plurality of secondarylight sources on the exit plane thereof, based on the exposure lightfrom the light source 1 a. The light from the optical integrator 93 a iscondensed by a condenser lens 4 a, which has the front focal pointlocated on the plane of secondary light sources formed by the opticalintegrator 93 a, to uniformly illuminate the field stop 95 a. The lightpassing through an aperture portion in the field stop 95 a then passesthrough a pair of plane-parallel plates 101 a, 102 a and a relay lenssystem 96 a, 97 a in this order to reach the mask 8. Here, the fieldstop 95 a and the surface of mask 8 are kept conjugate with each otherby the relay lens system 96 a, 97 a consisting of a lens unit 96 a and alens unit 97 a, and an illumination region MIa with uniformlight-quantity distribution is formed on the mask 8.

Thus, illumination regions MIa-MIe defined in a predetermined shape bythe field stops 5 a-5 e are formed on the mask 8, thereby illuminatingonly pattern portions in the illumination regions MIa-MIe on the mask 8.

Next, light from the pattern portions on the mask 8 illuminated by theillumination regions MIa-MIe travels through the five projection opticalsystems PLa-PLe provided in optical paths between the mask 8 and theplate 9 to form erect images of the pattern portions of mask 8 in theillumination regions MIa-MIe, as exposure regions PIa-PIe on the plate9. Since these projection optical systems PLa-PLe each have the samestructure, only the structure of projection optical system PLa isdescribed herein.

The projection optical system PLa has a triangular mirror member 98 ahaving a reflective surface 99 a inclined at 45° relative to the surfaceof mask 8 (YZ plane) and a reflective surface 12 a inclined at 45°relative to the surface of plate 9 (YZ plane), a lens system 910 ahaving an optical axis parallel to the surface of mask 8 and the surfaceof plate 9, and a roof reflective member 911 a having two mutuallyorthogonal reflective surfaces. Here, a ridgeline between the tworeflective surfaces in the roof reflective member 911 a is arranged tobe located at the position of the front focal point of the lens system10 a.

Such a projection optical system is disclosed, for example, in JapanesePaten Publication No. 49-35453.

Now, the light from the pattern on the mask 8 illuminated by theillumination region MIa is deflected 90° in optical path by thereflective surface 99 a of the triangular mirror member 98 a, thenpasses through the lens system 910 a, thereafter is reflected by theroof reflective member 911 a, and again enters the lens system 910 a.The light from the roof reflective member 911 a and through the lenssystem 910 a is deflected 90° in optical path by the reflective surface912 a of the triangular reflective member 98 a, and thereafter passesthrough the pair of plane-parallel plates 103 a, 104 a in the namedorder to reach the plate 9. Here, since in the projection optical systemPLa the image-forming relation in the Y direction is inverted by theroof reflective member 911 a, a real-size erect image of mask 8 isformed on the plate 9 even if the system is of a single image formation.

Although not shown in FIG. 58, the mask 8 and plate 9 are mounted onrespective stages movable along the Z direction in the drawing in theexposure apparatus according to the present embodiment. Then, moving themask 8 and plate 9 together while illuminating the mask 8 by theillumination optical systems ILa-ILe, real-size erect images of mask 8illuminated by the illumination regions MIa-MIe are serially formed onthe plate 9, whereby the pattern of mask 8 is transferred onto the plate9.

The present embodiment includes five sets of illumination opticalsystems and projection optical systems, but the number of sets ofillumination optical systems and projection optical systems is notlimited to only five. The illumination optical systems ILa-ILe in thepresent embodiment have the straight optical axes, but mirrors fordeflection of optical path may be provided in the respective opticalpaths of illumination optical systems ILa-ILe. Since the presentembodiment includes the plural illumination optical systems, withmechanical assembling errors there could arise a problem that the imagesof field stops 5 a-5 e are focused off predetermined positions on themask 8, i.e., that the illumination regions MIa-MIe deviate from thepredetermined positions. Thus, in the present embodiment, there areplane-parallel plates 101 a, 102 a to 101 e, 102 e provided asillumination region moving means in the optical paths of illuminationoptical systems ILa-ILe. The description continues by reference to FIG.59 and FIG. 60.

FIG. 59 is a drawing to show the XZ cross section of the illuminationoptical system ILa. FIG. 59 shows only the optical path from thecondenser lens 94 a to the mask 8. FIG. 60 is a YZ plan view to show theillumination regions being the images of field stops 95 a-95 e on themask 8.

In FIG. 59, the plane-parallel plate 101 a is arranged as rotatableabout an axis along the Z direction in the drawing, and theplane-parallel plate 102 a is arranged as rotatable about an axis alongthe Y direction in the drawing (the direction normal to the plane ofdrawing). Since the position of the rear focal point of the lens unit 96a is arranged so as to be coincident with the position of the frontfocal point of the lens unit 97 a, the relay lens units 96 a, 97 acompose a both side telecentric optical system.

Now, referring to FIG. 59, when the plane-parallel plate 102 a islocated at the reference position represented by the dotted line in thedrawing, that is, when the normal line to the plane-parallel plate 102 ais coincident with the optical axis of the illumination optical systemILa, there is no change in the relation between the field stop 95 a andthe image of field stop 5 a with respect to the optical axis ofillumination optical system. Next, when the plane-parallel plate 102 ais rotated about the axis along the Y direction from the referenceposition represented by the dotted line in the drawing to the positionrepresented by the solid line in the drawing, a light beam from thefield stop 95 a is horizontally shifted in the Z direction by theplane-parallel plate 102 a as shown by the solid line in the drawing,and thereafter enters the relay lens system 96 a, 97 a. The light beamfrom the plane-parallel plate 102 a and through the relay lens system 96a, 97 a reaches the mask 8 in the horizontally shifted state relative tothe optical axis of illumination optical system ILa (the optical axis ofthe relay lens system 96 a, 97 a). On this occasion, the image(illumination region MIa) of the field stop 95 a formed on the mask 8moves in the Z direction in the drawing. When the plane-parallel plate101 a is rotated about the axis along the Z direction in the drawing,the image (illumination region MIa) of the field stop 95 a formed on themask 8 moves in the Y direction in the drawing.

In the another embodiment, as described, the illumination region MIa onthe mask 8 can be moved within the YZ plane through rotations of thepair of plane-parallel plates 101 a, 102 a. Since the illuminationoptical systems ILb-ILe have the same structure as the illuminationoptical system ILa, the description herein concerned only the structureof one illumination optical system ILa.

Next described referring to FIG. 60 is an adjusting method where theillumination regions MIa-MIe by these illumination optical systemsILa-ILe deviate from the predetermined relation in the plurality ofillumination optical systems ILa-ILe because of errors upon assembling.In FIG. 60, in case of assembling errors existing in the plurality ofillumination optical systems ILa-ILe, the field stops 5 a-5 e arefocused, as the illumination regions MIa1-MIe1 as shown by the dashedlines in the drawing, on the surface of mask 8. When scanning exposureis made in such a state by moving the mask 8 and plate 9 along the Zdirection in the drawing, an illuminance distribution on the surface ofmask 8 cannot be uniform in the Y direction (the direction perpendicularto the scanning direction), causing variations in exposure amount on theplate 9. This will result in causing a problem that the linewidth ofpattern transferred onto the plate 9 is partially different.

Thus, in the method embodiment, the images of field stops 95 a-95 e aremoved from the illumination regions MIa1-MIe1 before adjustment to theillumination is regions MIa2-MIe2 indicated by the solid lines in FIG.60 by rotating the plane-parallel plates 101 a, 102 a-101 e, 102 e inthe illumination optical systems ILa-ILe about the axes along the Ydirection or the Z direction. On this occasion, the illumination regionsMIa2-MIe2 after adjustment keep a sum of lengths of illumination regionsin the Z direction (scanning direction) always constant at any positionin the Y direction. This can realize a uniform illuminance distributionin the Y direction on the mask 8, which can in turn make exposureamounts uniform on the plate 9.

Although the method embodiment is so arranged that the illuminationregions on the mask 8 are movable in two directions in the YZ plane, itis sufficient in order to obtain a uniform illuminance distribution onthe mask 8 that the illumination regions are arranged as movable atleast in the Y direction. Namely, a uniform illuminance distribution canbe achieved on the mask 8 as long as each illumination optical systemILa-ILe includes the plane-parallel plate 101 a-101 e rotatable aboutthe axis along the Z direction.

Since the another embodiment of the exposure apparatus has the pluralprojection optical systems PLa-PLe, the problem that the illuminationregions MIa-MIe are focused away from the predetermined positions on theplate 9 will arise if there exist mechanical assembling errors betweenthe projection optical systems. In that event, the problem of deviationof the exposure regions PIa-PIe from the predetermined positions willarise even if the illumination regions MIa-MIe are set to thepredetermined positions by the illumination region moving means in theillumination optical systems ILa-ILe.

Thus, the another embodiment of the exposure apparatus is provided withthe pair of plane-parallel plates 103 a, 104 a-103 e, 104 e as exposureregion moving means in the optical path of each projection opticalsystem PLa-PLe. This is next described referring to FIG. 61 and FIG. 58.

FIG. 61 is a drawing to show an XZ cross section of the projectionoptical system PLa, and FIG. 62 is a YZ plan view to show exposureregions being images of illumination regions MIa-MIe on the plate 9.

In FIG. 61, the plane-parallel plate 103 a rotatable about the axisalong the Z direction in the drawing and the plane-parallel plate 104 arotatable about the axis along the Y direction (the direction normal tothe plane of drawing) in the drawing are disposed in the optical pathbetween the triangular mirror member 8 a in the projection opticalsystem PLa and the plate 9.

Now, in FIG. 61, when the plane-parallel plate 104 a is located at thereference position represented by the dashed line in the drawing, thatis, when the normal line to the plane-parallel plate 104 a is parallelto the optical axis of projection optical system PLa, the relationbetween the illumination region MIa (not shown) and the exposure regionPIa (not shown) does not change relative to the optical axis ofprojection optical system PLa.

Next, when the plane-parallel plate 104 a is rotated about the axisalong the Y direction from the reference position shown by the dashedline in the drawing to the position indicated by the solid line in thedrawing, a light beam from the illumination region MIa is horizontallyshifted in the Z direction as shown by the solid line in the drawing bythe plane-parallel plate 104 a, and thereafter reaches the plate 9. Thismoves the exposure region PIa (an image of illumination region MIa)formed on the plate 9 in the Z direction in the drawing. When theplane-parallel plate 103 a is rotated about the axis along the Zdirection in the drawing, the exposure region formed on the plate 9moves in the Y direction in the drawing.

In the method embodiment, as described, the exposure region PIa on theplate 9 can be moved within the YZ plane by the operation of rotatingthe pair of plane-parallel plates 103 a, 104 a. Since the otherprojection optical systems PLb-PLe have the same structure as theabove-described projection optical system PLa, only the structure of oneprojection optical system PLa is described herein.

Next, in FIG. 62, if there are errors in assembling for the plurality ofprojection optical systems PLa-PLe, the illumination regions MIa-MIe onthe mask 8 are focused as exposure regions PIa1-PIe1, as shown by dashedlines in the drawing, on the plate 9. supposing scanning exposure ismade by moving the mask 8 and plate 9 along the Z direction in thedrawing, the illuminance distribution on the plate 9 is not uniform inthe Y direction (the direction perpendicular to the scanning direction),thus causing variations in exposure amounts on the plate 9. This willcause a problem that the linewidth of pattern of mask 8 transferred ontothe plate 9 is partially different.

Thus, in the method embodiment, the images of illumination regionsMIa-MIe are moved from the exposure regions PIa1-PIe1 before adjustmentto exposure regions PIa2-PIe2 shown by the solid lines in FIG. 62 byrotating the plane-parallel plates 103 a, 104 a-103 e, 104 e in theProjection optical systems PLa-PLe about the axes along the Y directionor the Z direction, as described above. On this occasion, the exposureregions PIa2-PIe2 after adjustment keep a sum of lengths of theillumination regions in the Z direction (scanning direction) alwaysconstant at any position in the Y direction. This can achieve a uniformilluminance distribution in the Y direction on the plate 9, which can inturn make exposure amounts uniform on the plate 9.

Although the another embodiment is so arranged that the exposure regionson the plate 9 are movable in the two directions in the YZ plane, it issufficient in order to obtain a uniform exposure distribution on theplate 9 that the exposure regions can be moved at least in the Ydirection. Namely, a uniform exposure distribution can be achieved onthe plate 9 as long as only the plane-parallel plates 103 a-103 erotatable about the axis along the Z direction are provided in eachprojection optical system PLa-PLe.

The another embodiment as described above includes the pair ofplane-parallel plates as the illumination region moving means or as theexposure region moving means, but instead thereof, a pair of angulardeflection prisms 105, 106 rotatable about the optical axis ofillumination optical system or projection optical system may beprovided, for example as shown in FIG. 63A. Also, for example as shownin FIG. 63B, a pair of angular deflection prisms 107, 108 movable in thedirections along the optical axis of illumination optical system orprojection optical system may be provided instead of the pair ofplane-parallel plates.

The present another may be so arranged that the field stop 95 a-95 e ineach illumination optical system is position-adjustable. In that case,for example by arranging the field stops 95 a-95 e as movable in the Ydirection and the Z direction, the illumination regions MIa-MIe formedon the mask can be moved along the two directions in the YZ plane. Also,the illumination regions MIa-MIe formed on the mask can be rotatedwithin the YZ plane, for example, if the field stops 5 a-5 e arearranged as rotatable about the optical axes of illumination opticalsystems ILa-ILe.

The embodiment shown in FIG. 59 has the field stops 95 a-95 e providedfor the respective illumination optical systems ILa-ILe, but anotherarrangement may be employed, for example as shown in FIG. 64, with asingle field stop 950 provided with aperture portions 950 a-950 ecorresponding to the illumination optical systems ILa-ILe.

Meanwhile, the another embodiments are arranged under the assumptionthat illumination variations caused by the illumination optical systemsand exposure variations caused by the projection optical systems areperfectly corrected. However, if there are, for example, fabricationerrors etc. in the illumination optical systems, illumination variationsappear on the mask 8, which could in turn cause exposure variations onthe plate 9. Even if the illuminance distribution is perfectly uniformon the mask 8, but if there are, for example, fabrication errors etc. inthe projection optical systems, exposure variations would occur on theplate 9.

Next described referring to FIG. 65A and FIG. 65B is a technique forcorrecting the illumination variations or exposure variations. FIG. 65Ais a plan view to show a field stop in illumination optical systems, andFIG. 65B is an enlarged drawing of the major part of FIG. 65A.

In FIG. 65A, the field stop has rectangular aperture portions 51 a-51 ethe longitudinal direction of which is the direction perpendicular tothe scanning direction (i.e., the Y direction), and checkered patterns,as shown in FIG. 65B, are given in overlapping regions in the Ydirection between the aperture portions 951 a-951 e (overlap regions).Here, the field stop has, for example, such a structure that chromiumpatterns are vapor-deposited on a plane-parallel plate and the checkeredpatterns are also formed by vapor deposition of chromium patterns. Theaperture portions 951 a-951 e are transparent portions.

For example, it there is a difference or illuminance on the mask 8between the illumination optical system ILa having the aperture portion951 a in the field stop and the illumination optical system ILb havingthe aperture portion 951 b in the field stop, the pitch of the checkeredpattern in the overlap region of the aperture portion 951 a may bechanged from that in the overlap region of the aperture portion 951 b soas to make the illuminance distribution continuous on the mask 8. Bythis, the exposure distribution can be made continuous on the plate 9.

If there is a difference in quantity of transmitted light between theprojection optical system PLa and the projection optical system PLb, thepitch of the checkered pattern in the overlap region of the apertureportion 951 a may be changed from the pitch of the checkered pattern inthe overlap region of the aperture portion 951 b so as to make theexposure distribution continuous on the plate 9. The checkered patternsdo not have to be limited to only in the overlap regions, but suchcheckered patterns may be formed in regions other than the overlapregions so as to make the illuminance distribution on the mask 8 or theexposure distribution on the plate 9 continuously uniform.

The checkered patterns as shown in FIGS. 65A and 65B may be replaced bydot patterns, for example as shown in FIGS. 66A and 66B. FIG. 66A showsa field stop having trapezoid aperture portions 952 a-952 e, and FIG.66B is an enlarged drawing of the major part of the aperture portions.As shown in FIG. 66B, dot patterns of chromium are provided in theoverlap regions in the trapezoid aperture portions 952 a-952 e. Here,the pitch, size, and location of each dot pattern are determined so asto make the illuminance distribution on the mask 8 or the exposuredistribution on the plate 9 uniform and continuous.

By this, the exposure amount can be always kept constant on the plate 9upon scanning exposure.

Instead of moving each illumination region by the illumination regionmoving means, an arrangement for attenuating a quantity of transmittedlight may be employed for portions in the field stop corresponding tothe overlap regions. In an example, the field stop is constructed byvapor-depositing chromium patterns on a plane-parallel plate, and dotchromium patterns are provided in the regions corresponding to theoverlap regions.

The above-described embodiments employed the lens system having thefront focal point at the ridgeline of the roof reflective member, as theprojection optical system, but any optical system may be employed aslong as it can obtain an erect image; for example, two Offner opticalsystems, two Dyson optical systems, or two refractive lens systemsarranged in series.

Further, the relay lens system in the illumination optical system may bea combinational optical system of a lens system having a plane mirror atthe front focal point thereof with a triangular mirror member, or acombinational optical system of an Offner or Dyson optical system with atrapezoid mirror member or right-angle prism.

Further, the another embodiment is provided with a plurality ofillumination optical systems corresponding to the individualillumination regions MIa-MIe, but instead thereof, another arrangementmay be such that for example, an optical fiber or half mirror is used toguide light from a light source or plural light sources to a pluralityof illumination regions.

As described above, the another embodiment can provide the exposureapparatus that can well transfer the pattern of mask onto the substratewithout causing a reduction of throughput and without causing exposurevariations.

Since in the another embodiment first and second illumination regionscan be moved on the mask by illumination region moving means, exposureenergy onto the plate can be always kept constant, for example, even ifthere are assembling errors for a plurality of illumination opticalsystems.

It is preferred in the another embodiment that at least one of the firstand second projection optical systems have the optical axis arranged asmovable relative to the optical axis of the other projection opticalsystem. This arrangement enables the pattern of mask always to beaccurately transferred to a desired position on the substrate. Supposingthe relation of optical axes on the mask side is not equal to therelation of optical axes on the substrate side in the first and secondprojection optical systems and even if the first and second illuminationregions are adjusted by the illumination region moving means so that thewidths in the scanning direction, of the illumination regions becomealways constant, positional relations in in-plane directions of maskwould be disturbed for an image (first exposure region) of the firstillumination region and an image (second exposure region) of the secondillumination region formed on the substrate with respect to the firstand second illumination regions, whereby the widths in the scanningdirection, of the respective exposure regions are not always constant.In this case, exposure amounts are not constant on the substrate, andthe linewidth of pattern transferred onto the substrate partiallyvaries, which is not preferred.

Since the exposure apparatus according to the another embodiment canrealize a large exposure area without increasing the exposure regions ofindividual projection optical systems, there is an advantage that theprojection optical systems can be constructed in a small size, and theprojection optical systems themselves can be easy to achieve highaccuracy. Further, because the optical members composing the projectionoptical system are compact in the exposure apparatus according to thepresent invention, generation of absolute aberration amounts can bedecreased, thus presenting an advantage that scanning exposure isrealized under excellent optical performance.

In the above-mentioned embodiments, the deflection of the mask 8 and theplate 9 caused by the gravity becomes small by setting the Y directionin the vertical direction.

As described above, embodiments according to the present invention areadvantageous in that a large screen can be exposed by single exposurewithout stitches in the screen and that a large exposure area can bescan-exposed by one operation without lowering the throughput and withexcellent imaging performance. Also, the projection optical systems canbe made compact in scale, so that high-accuracy projection opticalsystems can be readily fabricated.

Any embodiment as described above can be applied to any exposureapparatus described above. Further, the above described modificationadjusting member such as prism 105, plane plate 102 etc can be alsoapplied to any embodiment of the projection optical system and theabove-described illumination apparatus can be also applied to theexposure apparatus described above.

From the invention thus described, it will be obvious that the inventionmay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

The basic Japanese Application Nos. 161588/1993 filed on Jun. 30, 1993;345619/1993 filed on Dec. 22, 1993; 116800/1994 filed on May 30, 1994;123762/1994 filed on Jun. 6, 1994; 141326/1994 filed on Jun. 23, 1994;177898/1994 filed on Jul. 29, 1994; and 200494/1994 filed on Aug. 25,1994 are hereby incorporated by reference.

What is claimed is:
 1. An exposure apparatus comprising: a plurality ofprojection optical systems, each of the projection optical systemsprojects a predetermined pattern onto a substrate and forms an exposurefield on the substrate; and a substrate stage which holds the substrateand which moves in at least a scanning direction extending in a straightline; wherein the plurality of exposure fields are arranged along adirection crossing the scanning direction, and the projection opticalsystems and the substrate relatively move during a pattern projectingoperation along the scanning direction.
 2. The exposure apparatusaccording to claim 1, wherein each of the projection optical systems issubstrate side telecentric.
 3. The exposure apparatus according to claim2, further comprising an illumination system which supplies illuminationlight to the plurality of projection optical systems.
 4. The exposureapparatus according to claim 2, wherein the plurality of exposure fieldsare aligned in first and second columns extending in a directioncrossing the scanning direction, and the first and second columns arealigned with different positions in the scanning direction.
 5. Theexposure apparatus according to claim 4, wherein each of the projectionoptical systems has a field of view, and the plurality of fields of vieware arranged at different positions on a mask.
 6. The exposure apparatusaccording to claim 5, wherein the mask is movable in the scanningdirection.
 7. An exposure method comprising the steps of: forming aplurality of exposure fields using a plurality of projection opticalsystems, each of the projection optical systems projects a predeterminedpattern onto a substrate; and exposing the pattern onto the substratewhile moving the substrate along at least a scanning direction extendingin a straight line; wherein the plurality of exposure fields are alignedin a direction crossing the scanning direction.
 8. The exposure methodaccording to claim 7, wherein each of the projection optical systems issubstrate side telecentric.
 9. The exposure method according to claim 8,wherein the plurality of exposure fields are aligned in first and secondcolumns extending in a direction crossing the scanning direction, andthe first and second columns are aligned with different positions in thescanning direction.
 10. The exposure method according to claim 9,wherein each of the projection optical systems has a field of view, andthe plurality of fields of view are arranged at different positions on amask.
 11. The exposure method according to claim 10, wherein the mask ismovable in the scanning direction.
 12. The exposure apparatus accordingto claim 1, wherein the projection optical systems each havingprojection error corrector which is disposed in an optical path of theprojection optical system and which corrects an optical error of theprojection optical system.
 13. The exposure apparatus according to claim12, wherein the optical error of the projection optical system includesan error due to environmental changes.
 14. The exposure apparatusaccording to claim 12, wherein the optical error of the projectionoptical system includes at least one of a magnification error and animage position error.
 15. The exposure method according to claim 7,further comprising a step of correcting an optical error of theprojection optical system.
 16. The exposure method according to claim15, wherein the optical error of the projection optical system includesan error due to environmental changes.
 17. The exposure method accordingto claim 15, wherein the optical error of the projection optical systemincludes at least one of a magnification error and an image positionerror.
 18. An image projection apparatus comprising: at least one lightsource; a plurality of illumination optical systems; a plurality ofprojection optical systems, each of the projection optical systemsprojecting a predetermined pattern onto a predetermined plane based on alight from one of the plurality illumination optical systems; and alight guide arranged along an optical path between the at least onelight source and the plurality of illumination optical systems, andhaving at least one input end which optically connects to the at leastone light source and a plurality of output ends, wherein each of theplurality of output ends optically connects to one of the plurality ofillumination optical systems.
 19. The image projection apparatusaccording to claim 18, wherein the at least one light source comprises aplurality of light sources.
 20. The image projection apparatus accordingto claim 19, wherein the projected predetermined patterns partiallyoverlap each other.
 21. The image projection apparatus according toclaim 18, wherein the predetermined pattern is arranged along an opticalpath between the illumination optical system and the correspondingprojection optical system.